It only takes a couple of clicks, maybe a single keypress to accidentally delete a vital file. If you clear the Recycle Bin before you notice (or the file never makes it there, because it's deleted by a virus), then all that work is gone forever.

Well, maybe not. Install O&O UnErase, and it'll scan your entire hard drive to track down every deleted file. Select the files of interest, click Restore, and the program will try to recover them. This isn't always possible, because sometimes part of the file will be overwritten by something else, but UnErase will retrieve whatever it can.

You've already got a file that needs to be recovered? Then don't install UnErase immediately, because that in itself could overwrite your data. Install the program on a second PC instead, and launch its InstantUnerase feature. This lets you start UnErase from a disk, so you can recover files without having to write anything to your target system.

UnErase can find thousands of files on large drives, so you might find it takes a long time to scan your system. If you need to improve performance, click Action > Advanced Search, and tell the program to search for particular file names, creation date or size.

Note that the trial version only finds possible files for undeletion. It doesn't actually restore old data.