You should check out this free file recovery program...
PC INSPECTOR File RecoveryWhen files are deleted, they are not erased, the file system just removes them from the file table and marks the space on the drive that they occupied as "available".
Everything you do on your computer is writing files to the hard drive that may overwrite your data files if they are still there.
When you lose files, the best thing to do is immediately shut down the computer, remove the hard drive, connect it as a secondary drive on another computer and run the file recovery software linked above on that computer to recover the files from your drive.
I had the same thing happen to me recently. I just bought and installed a new 120GB Seagate hard drive and began
moving many, many gigabytes of files onto it. about an hour into the process, the new drive completely failed.
Using the process above, I was able to recover
most of the files from my original drive. Some of the casualties were large VOB and CHD files that were over 1GB each. The larger the file, the more likely that one of it's clusters will be overwritten after it is deleted. Also, if you keep your drive thoroughly defragged, it's supposed to be less likely that writing to the drive will overwrite multiple deleted files.
The one big lesson I learned in this ordeal...
NEVER move files
ALWAYS copy files
...that way, if something goes wrong, you still have the original copy.