Topic: Backing Up Data
Target Audience: All
Author: Oracle128
Written: 7 Mar 2006

Your data is important. Hundreds of documents, downloaded files, game saves. Contact lists, emails and appointments. Then your hard drive gets corrupted, or even worse, mechanical failure. Hard drives are delicate devices, after all. You try and try to get your data back, but you just keep denying the truth - you've lost it all. All that hard work, late nights, used-up download allowances, gone forever. Hard drives can and do fail like any mechanism, that's inevitable, and there's nothing you can do about it. What you CAN do is be prepared for it, by making a dead hard drive have only a minor impact on your PC operating routine, and the way to prepare yourself is by backing up.

What Can Go Wrong?
There are many things that can go wrong to make you lose your data. These include: There are also times when you plan to backup before something you do manually, like:
How To Backup
Ghosting
Ghosting is a term used to mean the process of capturing a complete image of a drive's contents and storing this image file elsewhere for safekeeping. While the term originally applied to an actual disk cloning utility called Ghost (now owned by Symantec under the name Norton Ghost), the term is now applied in the verbal sense ("to ghost"), which may be done by a similar alternative program. Also referred to as "drive cloning" or "drive imaging" (with the stored data referred to as the "image").
Pros: Cons: Backup Utilities
Backup utilities (other than disk-cloning or ghosting utilities) can make backups easy and quick. The are hundreds of backup utilities available, both free and commercial. Try here for a start. Major software companies specializing in security software (such as Symantec) usually also sell various backup utilities. Simple backup processes can also be scripted using the operating system script files (such as Windows batch files) as a simple alternative. The other advantage of a script file is you may be able to incorporate a command-line compression utility to compress the backup files. The backup features you'll get will depend on what backup utility/scripting language you use, so the following is a generalized list.
Pros: Cons: Synchronizing Utilities
Synchronizing is very similar to backing up, except instead of copying specified files to safe storage, two or more storage locations are synchronized, keeping all storage devices up to date with the latest versions of files only when necessary. For example, if you had a home network, you could keep your personal documents folder synchronized with a duplicate folder on another computer in your network. You can add/modify files on either computer, and only the newest version will be synched over the network (most sync utils allow setting up of rules to determine which file to keep should the file be modified at multiple locations since the last transfer).
Pros: Cons: RAID
RAID is a way of mirroring and/or combining the power of multiple hard drives within the computer. It is described further in the section detailing different storage mediums.
Pros: Cons: Manual Copying
Using the operating system you can simply select which files you want to backup, and copy them to the storage device manually (eg. drag and drop). This requires no additional software, but is the worst method to use.
Pros: Cons:
What To Backup
What you decide to backup is up to you, but the following list will help you get started, and may remind you of things you haven't yet considered.
Where To Store Backups (The Storage Medium)
The storage media available to you will depend on several factors, such as budget, available resources, technical expertise, and storage requirements. A major point to make is that you aren't always limited to a straight 1:1 copy of your files; you can always compress them with file compression tools.

Another issue that needs to be addressed when backing up for extended periods of time (eg. several decades) is whether or not that medium will be readable at that time. All kinds of technologies become obsolete eventually, and data storage technologies are no different. You might find that you can no longer find <disk drive> to read that important data you stored on <storage medium> in 30,40,50 years time. There are some great articles on this topic at Business Week ("Safe Storage -- for How Long?") and Sydney Morning Herald ("The digital Dark Age"). Also check out the comments on the latter article in this Slashdot post.

Below we will examine several storage options. Each has a table showing its strengths and weaknesses in various categories. These are:
Longevity - How well the medium can store data over long periods, including the viability of future connectivity.
Reliability - How reliable the medium used is (can data be randomly corrupted? affected by electro-magnetic interference? etc)
Safety - How well the backup method protects against various potential data loss events, including fragility of the medium
Capacity - Larger storage mediums score higher
Speed - Storage mediums that have higher rates of data transfer and physically allow for making backups faster score higher
Cost - Cheaper storage mediums score higher

Partitions
A partition is a way of making one hard drive act like several drives. While separate partitions are a great way to keep data organized better than with folders, they can also be used to separate application installs and personal file storage separate from the operating system installation. Data can be transferred between the two (or more) logical drives, and if the operating system or drivers become corrupt, you can format the system partition without affecting data on the other partitions. Extra partitions can be used to temporarily store data from other partitions while they're formatted. Partitions work by physically separating the location of the data storage on the drive's platter into different sections, and virtually representing them as different drives. Partitions can be managed by the operating system (eg. Windows XP's Disk Management utility) or by separate software (eg. Partition Magic).

  Excellent Good Average Bad Poor
LongevityX    
Hard drives can store data well for long periods, and are the least likely of the discussed mediums to become obsolete.
Reliability X   
Though data can occasionally become corrupt, hard drives keep data fairly reliably.
Safety    X
Partitions are only as good as the hard drive they're on; if the drive fails or is destroyed, you lose all it's partitions.
Capacity X   
Hard drives are one of the largest capacity storage mediums, widely available (at the time of writing) in 160GB, 200GB, 250GB, 300GB or 400GB capacities. However, partitions merely separate the space, and don't provide any additional space on which to backup.
SpeedX    
Moving data from one section of a hard disk's platter to another is about the fastest method of data transfer, and the backup partition is always available whenever the main partition is.
CostX    
Partitions require no additional purchase, but at the price of using capacity from the primary partition.

Internal HDD (Slave)
A second (or third, fourth etc) hard drive is a better alternative to a partition; rather than having multiple virtual drives off the one physical disk, you have several physical drives. While keeping backups on a separate drive, you have better safety if one of them fails. Note that, in this sense, 'slave drive' does not necessarily mean the drive has to specifically be configured in the 'slave' configuration. Whether it is a slave drive, a master drive on another IDE channel, or a SATA drive (which doesn't have the concept of 'Master/Slave') makes no difference.

  Excellent Good Average Bad Poor
LongevityX    
Hard drives can store data well for long periods, and are the least likely of the discussed mediums to become obsolete.
ReliabilityX    
Though data can occasionally become corrupt, hard drives keep data fairly reliably.
Safety  X  
While an additional hard drive may protect against mechanical failure or (possibly) data corruption, events that effect the primary drive may affect additional drives due to close proximity.
CapacityX    
Hard drives are one of the largest capacity storage mediums, widely available (at the time of writing) in 160GB, 200GB, 250GB, 300GB or 400GB capacities.
SpeedX    
Probably the next best thing to transferring data from one section of platter to another on a single drive (partitions) is transferring from one internal drive to another. The Serial ATA version 2 (SATA-II or SATA300) interface or later is preferred. The backup partition is always available whenever the main partition is.
Cost X   
Hard drives provide one of the best cost/capacity ratios.

External HDD
An external hard drive is almost the same setup as an internal hard drive; the difference being the hard drive is contained in an 'external enclosure', and connects to the computer via USB, FireWire (aka iLink or IEEE1394) or Serial ATA, depending on the connections supported by the enclosure (some enclosures have more than one). Having data on an external drive makes it easier to separate the drive from the PC when not in use, and store it somewhere for safe keeping.

  Excellent Good Average Bad Poor
LongevityX    
Hard drives can store data well for long periods, and are the least likely of the discussed mediums to become obsolete.
ReliabilityX    
Though data can occasionally become corrupt, hard drives keep data fairly reliably.
Safety X   
Assuming the drive is kept well away from the PC when not in use (see "Where to store backups (Location)"), external hard drives allow for the best safety due to their portability. They are only let down by their fragility.
CapacityX    
Hard drives are one of the largest capacity storage mediums, widely available (at the time of writing) in 160GB, 200GB, 250GB, 300GB or 400GB capacities.
Speed X   
While it depends on the connection interface used, external hard drives are generally slower to transfer than internal drives. Additionally, their accessibility when stored away from the PC makes them more inconvenient.
Cost X   
Hard drives provide one of the best cost/capacity ratios, and external enclosures are quite cheap. It's recommended to buy the drive and enclosure separately, rather than as one unit. This can save quite a lot of money, and ensures you get the combination of disk capacity and enclosure features required.

CD-R/RW
Compact Discs have been around for many years, and CD burner drives are available for about the cost of a printer ink cartridge or two. With CD-R media (R for "Recordable"), you can only recorded data, and that data is on there for the rest of the disc's lifetime. You can keep adding data to the disc until it's full, but any data recorded to it cannot be erased. They can be bought for much less than a cup of coffee each, but are usually bought in bulk (spindles of 25 or 50) to save more. CD-RW discs ("Re-Writable") can be written to and erased as many times as the media physically allows. This is usually about 100 times, but can be more or less depending on brand and quality. They cost about twice that of CD-Rs.

  Excellent Good Average Bad Poor
Longevity X   
The longevity of burnt CDs has been under debate for quite some time. While some CD-R media is rated as lasting 100 years (roughly equal to commercially-produced CDs), rumours and speculation have suggest some brands of discs can last as little as 5-10 years. While CD-Rs will generally last longer than RWs, you should spend more money on better quality brands (such as Verbatim) to stay safe. With the low price of CD media, burning multiple copies of the same data is completely practical.
Reliability X   
Burnt CDs are prone to errors, but usually the complex error correction of the CD format negates this. Higher burning speeds allow for more errors, so important data should be burnt at lower speeds, if not the lowest possible, to avoid them. One thing to note is that when copying/burning across several generations (ie. burning a copy of a copy), these errors can build up and potentially cause unreadable data. The One-to-One nature of digital data doesn't necessarily apply to CDs. Like above, multiple copies of the same data (in one generation) is practical.
SafetyX    
The ability to store several copies across several locations, and the general durability of optical media, give CDs a high score in this category.
Capacity   X 
CDs are available in 650MB (70 minutes of CD Audio) or 700MB (80 minutes) capacities. While this was quite large when CDs (and eventually CD-R/RW) first entered the market, this becomes less practical in todays world of high-definition, high resolution, high bandwidth internet and higher expectations.
Speed   X 
CD burning is limited by several factors, but mainly two things: the physical speed the disc can be spun before centrifugal forces start to warp, crack, and eventually shatter it; and the speed at which the laser can accurately burn data onto the disc. For this reason, CDs should be burnt at lower speeds, however even at higher burn speeds, data transfer from source to CD is among the slowest. Also, the effort it takes to arrange files to fit better on to the discs, and the manual process of burning the CD, insert another blank CD etc. is time consuming.
CostX    
As mentioned, CD burners are one of the cheapest PC components you can buy, and the minimal cost of CD media is a big advantage.

DVD+/-R/RW
DVDs (also unofficially known as Digital Versatile Discs) are similar to CDs in almost every aspect bar two; a) they have a more complex structure and can hold more data which makes them b) slightly more expensive. Blank DVDs come in various formats: The 'dash' (DVD-R/RW/DL) and 'plus' (DVD+R/RW/DL) formats are slightly different, but almost all fairly current DVD burners support both. The R (recordable) and RW (re-writable) varieties are the DVD versions of CD-R/RW, with R being recordable only once, and RW able to be written to/erased many times. All of those formats of DVD store 4.7GB of data. The DL ("dual layer" for DVD-R, "double layer" for DVD+R) stores data in two layers, and provides nearly twice as much storage at about 8.5GB. DVD-RAM (DVD Random Access Memory) is a special format supported in very few drives. It allows for repetitive read/write access to the disc, treating it somewhat like a hard drive. DVD-RAM has between 2.58 to 9.4GB capacity, depending on the DVD-RAM version and if it's single or double sided. DVD+/-R/RW cost about 60%-100% more than their CD counterparts (with little, if any difference between + or -), while DVD-RAM discs cost a fair bit more.

  Excellent Good Average Bad Poor
Longevity X   
Similar to CDs
Reliability X   
Like CDs, DVDs can also get errors during the burn process, especially at high speeds.
SafetyX    
For the same reasons as CD.
Capacity X   
Next to hard drives, dual layer DVDs are one of the highest capacity media.
Speed   X 
DVDs suffer the same physical and logistical issues as CDs (eg. burn process, swapping discs)
Cost X   
While standard DVD+/-R media are comparable in cost to CD-R, expect to pay several times more for dual layer discs or DVD-RAM.

Network Storage
By transferring your data to a network-attached PC, you can save time and money. However, the cost is that you'll need a second PC to connect to the network and receive the files, or a Network Attached Storage (NAT) device which does the same job, but nothing else. The network could be a home LAN with the backup device in a separate area of the house, or over the internet, with the backup device anywhere in the world for more security. Usually, the backup device uses hard drives for storage, so the scores below will reflect that.

  Excellent Good Average Bad Poor
LongevityX    
Assuming the backup device uses hard drives
ReliabilityX    
Assuming the backup device uses hard drives
Safety X   
There is a slightly higher risk involved, since data can be lost or corrupted during transfer. More dangerous over longer distances. Most times, the errant data is detected and sent again
CapacityX    
Assuming the backup device uses hard drives
Speed  X  
This depends highly on what kind of network is used for transfer. For a local, wired connection, the standard 100Mbps transfer is quite adequate, and would score a 'good'. However, the setup is more efficient if a wireless, or an internet connection is used. Either of these puts limits on the transfer speed, and this results in a slightly lower score
Cost   X 
The cost of this setup includes the backup device (NAT or a second PC), the storage for that device, plus the cost of bandwidth (a major factor when transferring via internet)

Internet Storage
For the simple and convenient storage of smaller files, they can simply be e-mailed to your own account, or uploaded to your own web host (such as the free web site that many ISPs give you). Like network storage, there is a good chance that the data will be stored on hard drives. However, these methods are less secure since they are not managed by yourself, and you are usually given no guarantee as to the safety of your data when stored in this way.

  Excellent Good Average Bad Poor
Longevity   X 
This method is only for quick storage when there are no other options available. The data itself MAY be safe for many years, but this is a risk that should be avoided
Reliability  X  
You should only use this method for temporary storage when there are no other options. The low reliability is a result of the uncertainty involved in using this method
Safety   X 
Since e-mail or web hosting are managed by a third party, there is a higher risk involved as this method is not being used for it's intended purpose (e-mail or web site storage). However, the more you pay for your web hosting, the safer it's likely to be
Capacity   X 
If you pay for web hosting, you probably have adequate storage space to store your files in an emergency. However, despite the larger inboxes of free e-mail/web hosting accounts these days, they aren't likely to be large enough
Speed   X 
Backup must be done manually (ie. no automation), transfer over the internet is relatively slow (even with broadband), and there's a good possibility you'll have to split your files into smaller chunks due to account limitations
CostX    
A web-based e-mail account, such as Google Mail, Hotmail or Yahoo! is free, and might be all that you need to conveniently backup a few files

RAID
RAID (Redundant Array of Independent Disks) is a way to keep data actively backed up. It requires multiple hard drives, and a RAID Controller - these can be found built in to modern motherboards (especially those with SATA support), and you can also buy separate RAID controllers for PCI slots. Motherboards with built-in RAID often come with RAID levels 0,1,0+1,5, and often JBOD. The full definition and description of RAID is beyond the scope of this document. You can get more information on RAID and it's various levels in this Wikipedia article. There are also many good references for RAID information when searching the internet.

While some of the RAID levels is an excellent way to keep data safe from mechanical failure or data corruption, RAID is not designed as a storage space to backup your data in times of need. Thus, a RAID solution should be planned and implemented well before disaster is likely to strike. RAID is easiest to setup before you fully use the main drive, but additional drives can usually be added to the array at any time. How and when they are added, and how many should be added at one time, depends on the level of RAID used.

  Excellent Good Average Bad Poor
LongevityX    
RAID (usually) uses hard drives for storage, which provide the best longevity available.
ReliabilityX    
With the possibility for multiple mirrored copies of data, most levels of RAID keep the data reliably.
Safety X   
Whilst RAID gives the best protection from drive failure or data corruption, it receives a lower score here because of the simple fact RAID is not designed to assist in storing data in a remote location, which would prevent from natural disasters.
CapacityX    
Hard drives have the largest capacities available. Some RAID levels also provide methods for joining multiple drives together to form one logical disk, but this detracts from the 'mirroring' side of RAID.
SpeedX    
Hard drives have the fastest read/write speed available. Some RAID levels also have features to space data out across multiple drives, reducing I/O time so the system spends less and less time waiting for the drive/s to deliver the data, bringing it closer to the speed in which the motherboard can deliver the data through the IDE/SATA connections, and the CPU can handle it.
Cost  X  
Though hard drives provide the cheapest cost per capacity, the better RAID levels (level 0+1 and level 5) work best with more hard drives. Depending on the RAID schema used, you may also be allowed to only add a set number of drives at a time.

USB Flash Drive
USB flash drives are small, highly portable devices which use solid-state memory (doesn't require power to store, only to use) to store data. They can work on any system (PC, Mac, or other electronic device) that has a USB port. The standard "USB Mass Storage Device" (almost any USB storage device) drivers are included in the core operating system of Windows ME, 2000, XP and above, Mac OS 9 and above, and Linux 2.4.6 and above. Drivers are most likely available for earlier or alternate operating systems, either included with the device, or downloadable from the internet.
  Excellent Good Average Bad Poor
Longevity  X  
Flash drives are designed for portable, temporary storage, usually for simply transferring documents between different machines. While they can and will store data safely for several years, they are known to eventually corrupt data, or simply fail completely, whether it be internally, or in the USB interface mechanism. The USB interface itself is an open standard and widely popular, so is likely to be around for a long time - if not, easily enough replicated if needed assuming the specifications are still available.
Reliability X   
Over the short term, flash memory provides great stability. Marked down because of slight unreliability transferring data over the USB interface.
Safety X   
Great safety from disaster, only marked down because USB drives are too portable, making them easily lost, misplaced, forgotten or stolen.
Capacity   X 
USB flash drives are these days available in sizes ranging from 256MB to 2GB. This places them at an average about equivalent to CD storage.
Speed  X  
Whilst some older USB drives transfer at USB 1.1 speed, 12Mb/s, most drives support the USB 2.0 interface, running at 480Mb/s (theoretical maximum). It is likely the drive is limited to it's internal memory's read/write speed rather than the USB transfer limit, but this varies depending on the technology used.
Cost    X
Flash memory has one of the worst cost per capacity ratios of all storage mediums, only slightly better than system RAM.

Others
You may have noticed a few other storage possibilities missing, such as floppy disks, tapes, and zip disks. I have deliberately left these out; floppy disks are too small for realistic backup, are now considered obsolete, and may be difficult if not impossible to find. Additionally, many PCs now come without floppy drives. Magnetic tapes and drives are expensive, require many tapes for redundancy (because of their high chance of failure), but have fairly high capacity. They are used mainly for businesses that have to keep many redundant copies of large-capacity data, and aren't readily available to regular consumers.

Where To Store Backups (Physical Location)
Another major factor of backup is where to store your backups once they've been transferred. Physical location is important for protecting mainly against natural disaster - fire, flood, blizzard, hurricane, tornado, electrical surges (and lightning), you get the idea. It's also important to separate your backup data from your PC due to the possibility of damage (eg. dropping a laptop), malicious access, or loss/theft.

It's also important to note that some backup methods/storage mediums don't allow for easy portability of the backup. Removable discs and USB flash drives are highly portable. External hard drives are somewhat portable, but are very fragile. RAID, internal hard drives, and partitions are difficult to impossible to make portable.

Close To The PC
Simply moving the backup slightly away from the PC (ie. anywhere in the same room except on or inside the PC) is good enough for a simple backup, assuming your geographic location doesn't frequently suffer from disasters, natural (eg. weather) or man-made (eg. war). The further away, the better, and that applies to the other possible locations too. Keeping your backup data close may be more convenient if you frequently lose it, and is also a good idea if you think you're going to forget where it is otherwise.

Further Away From The PC
Again, the further the better. Moving the backup to the other side of the room your PC is in, or to the other side of the house will be enough to cover smaller disasters.

Fire/Water/Electricity/Magnet Proof Safe
The more elements the safe protects against, the closer you can have it to the PC without it being any safer. Magnetic-proof (protect from electromagnetic interference) and electricity-proof (protect from lightning) safes are difficult to find and quite costly. Water-proof/water-tight safes (protect from flood, storm) are a little easier to obtain and don't cost much more than a fire-proof safe. Fire-proof safes (protect from fire) are good enough if you don't live in a particularly bad-weather-prone area, though you need to take into account how hot the safe gets internally. Having a fire-proof safe is no good if the drive inside is going to melt anyway after just a couple minutes surrounded by fire.

Another Building
If you're on good terms with your neighbours, store your backup at their place. Maybe you could even setup a "backup-trading routine" for your street - house 1 stores their backup in house 2, house 2 stores in house 3, house 3 stores in house 1. Again, the further the better; if you have a whole street of houses, have each house store their backup across the street and two house down. Got a friend or relative in the same city as you? Ask them to keep your backup. There are also extreme methods; for example, this company, who rent web/data servers operated in an abandoned Cold War era nuclear bunker. Obviously this is intended for major corporations such as banks, and is beyond the reach of individuals; but it gives you an idea of the lengths you can go to for data protection, with the right resources.

Safety Deposit Box
You can often rent a safety deposit box relatively cheaply from your local transport hub (the typical "locker at the train station" you see on TV), bank, or possibly news agent or post office. This most likely provides the safest protection for the cost, but depends on how important your data is, how often you take the backup there (you'll need a 'swapping' system), and how convenient the location is. Renting a deposit box at the bank down the street will do no good if a flood, hurricane or tornado comes through your area, but it also won't be a good idea to drive 3 hours to the box to swap the storage over to the latest backup every so often.

When To Backup
Backing up once isn't good enough. One of the best backup strategies is to set a schedule to backup regularly, with the best strategy to backup instantaneously (such as through a RAID setup, or directory synchronizing utilities). The schedule could be anything from every hour, to once a month. How often you do backup is determined by how much you're committed to backing up, how important the data is (you may classify different levels of importance for different types of files, backing them up with appropriate frequencies), and the medium/method you use to backup plays a part too (burning several DVD RWs full of data every hour would be quite difficult).

You may also choose to backup only at key points. In a similar way to how Windows XP sets a restore point when installing drivers, Windows components, and larger applications, you can do the same; backup before you make a major hardware or software change (eg. installing RAM, upgrading operating system), backup after the change, or backup after you've made significant changes to an important document.

Backup Strategies
There a several different strategies you can implement to choose how you backup data. These are:

Incremental Backup
Backing up only those files which have changed or been created only since the last backup.

Synchronized Backup
Having a setup which synchronizes the backup copy based on the original. This can be implemented with hardware or software, and can be instantaneous, scheduled, or event-driven (initiated by the user, a detected change in the system, or performed whenever the backup media is accessible). Using this strategy, there are several options you can use for synchronizing, depending on how it's implemented. Some sync software will allow you to choose what to do with conflicting copies of files, but these options are only useful if both synchronized copies may be in use simultaneously.

Complete Backup
This implies a simple straight copy of your original files to the backup storage (whether they be specifically chosen for backup, or a complete drive image).

Recovering Backups
The actions you need to take to restore a backup are as important as those you need to take to create the backup. A convenient backup plan is no use if you have to jump through hoops just get your data restored to the way it was before it was lost. There are three main ways a backup is restored:

Copy The Data Back
Simply copying the data back to the original location may be all that's necessary. If you have lots of different files belonging to different locations, it may be an idea to keep note of which files belong where - a text file, or even better a database. Alternatively, keep the same directory structure in your backup as the original files have, that way you can simply copy over the root backup folder. You will first have to reinstall the operating system, then load on all the applications you had on before. Once done, you can copy across the user and data files. The Windows registry, and many system files (Windows or other operating systems), may need to be restored either in Safe Mode (or equivalent), or with a boot utility, such as the Windows Recovery Console.

Automatic Restore
Any backup program you use to backup may keep the original file/directory locations itself in a file (you'll need to backup this file as well). If you used a script file to backup, use a similar one to restore - simply switch the source and the destination.

Boot Disk
If you used a ghosting or disk imaging tool to backup, they will usually generate a boot disk (floppy, CD, DVD, USB drive etc) which you can use to restore the system without first having to restore the operating system. To use, first make sure the drive relevant to the boot disk used is available to boot with in the BIOS. If none of those bootable drives have an operating system on them, the Boot Order will not make a difference. Otherwise, you may need to set the drive you want to boot from higher in the boot order than the primary hard drive.

Recovery With No Backup
This whole document has been about how to backup your data to prevent loss. But what can you do if you lose data and haven't been backup? There's a few things you can try, but depending on what's happened to make you lose data, you will have varying levels of success. The scope of this document doesn't cover data recovery in full, but it will list and briefly outline some of those options.

Was It Really Deleted?
Windows has a 'Recycle Bin' visible on the desktop, and many operating systems have a similar 'trash can' setup; this is where "deleted" items go when you use the graphical interface (eg. Windows Explorer) to delete them. In here, they're not really deleted, they've simply been moved to a special folder, ready to be deleted. Files are not deleted until you empty the bin, though some operating systems are configured to automatically empty it every so often, or once it reaches a certain size. Even once files are deleted in this way, they aren't actually removed from the drive - the drive file structure marks the space the file used as 'available', and the operating system can then use it to store other data. Thus, the first step to take if you accidentally delete data is to stop writing files to the drive, or even better stop using the computer and take it to someone who knows what to do.

Recovery Software
There are many applications you can download that will attempt to recover lost data. Firstly, these should not be installed on the same drive you wish to recover from, for the reasons stated above. Secondly, it's best to try a combination of data recovery software. Some might recover everything, some might recover nothing. You might get half your files back with one, and the other half with another tool. As mentioned before, you'll get various success, and a lot of it comes down to luck.

Secondary Drive
In cases where the data is partially/completely intact, but the operating system on the drive will not load, it's possible to access the drive's contents another way. By removing the drive from where it is, you can either place it in another, working, system, as a secondary drive, which can be accessed the same way any other drive is. From there, you can copy working files across, and make attempts to recover others.

Linux
You've probably heard of Linux by now; it's the open source (and free) operating system that's competing with Windows. No matter what operating system you run, you can create a boot CD that will load a Linux distribution long enough for you to recover your data any way you can. The most popular distribution for data recovery is Knoppix, available here. Knoppix is an operating system on a CD, which means that, like above, you can easily use it in instances where the installed operating system won't load. Out of the box, Knoppix has support for the file systems used by Windows (FAT32, NTFS), and will also support a variety of methods for relocating this data; other drive partitions, other drives, shared network folders, floppy disk, USB storage, even the internet. Burning recovered files to CD/DVD can be done, but requires a second CD/DVD drive in the computer (since the Knoppix disc needs to remain in the drive at all times).

Additional Resources
The following is a list of helpful resources for data backup and recovery: