File recovery relies on the fact that when a user deletes a file (or empties the wastebasket or recycle bin) the contents of the file aren’t physically obliterated on the disk, but rather the file is simply flagged as deleted. More precisely, the space it occupies is marked as available for writing. This means that the older the file, the less chance there is of successful recovery because it’s more likely to have been overwritten by another newer file.

File recovery software works best when the deleted files are recovered to another drive. That's because the very act of recovery involves writing to your drive, and you don't want to write over other files yet to be recovered. The "other" drive can be another hard disk, another hard disk partition, a networked machine, or an external USB device.

Recovery programs operate more successfully if they are installed before any file recovery is attempted. If the file you want to recover is on your “C” drive, the simple act of installing one of these programs onto that drive may obliterate the target file you want to recover. Remember that recovery software cannot undelete files that have been written over.

Recovering data from physically damaged drives is also beyond the capabilities of most free recovery tools.  There are tools that will attempt partial recovery, but generally these are expensive commercial products or services.

However, if you have just accidentally emptied your wastebasket (recycle bin), or explicitly deleted a file, and realized you’ve made a mistake, file recovery is a very real possibility. The golden rule is “don’t write ANYTHING to the disk, or reboot”. Just immediately run your recovery software.

Until recently, file recovery was one of the few categories where the main commercial products really outshone the freeware alternatives. Good examples of commercial products include the impressive "R-Studio”, “Recover My Files”, and “Active File Recovery.”

But recently the picture has changed dramatically. You now have some excellent freeware choices:

Brian Kato's Restoration works with FAT and NTFS file structures and requires no installation, which means you can run it from a USB drive, CD or floppy. Unfortunately, there appears to have been no recent development work on this product. Brian's web site is not currently working so this is a direct download link to the SnapFiles download site.

Recuva, from the makers of the highly regarded CCleaner, is now probably the best choice for many users who want a quick simple solution. It also copes well with the flash memory used in digital cameras, MP3 players, or USB drives.

But my top selection is PC INSPECTOR File Recovery. It's aimed at slightly more technically-advanced users but produces very impressive results. Indeed, everything about this program is impressive and it poses a direct challenge to its commercial rivals. It neatly distinguishes between physical and logical drives, has excellent file search capabilities, and even allows you to search ranges of specific clusters. Works happily on Vista although it’s only specified as “up to XP”. 

PC INSPECTOR File Recovery is a truly outstanding professional product. I suggest you install it just in case you may need it (and while it remains free).