Use some file recovery software and scan the drive for them.
The main thing is DO NOT ALLOW
any more write operations on the drive in question.
If this happens to be the default system drive then your chances of recovering the files in their entirety have plummeted a fair bit - a very good reason why you don't keep your data on the system partition/drive.
- download the portable build and extract it to a flash drive and then run. Recover to a separate drive, (not the one you're recovering from). PhotoRec
- very good also.
If it was your system drive they were on, turn off the computer, go to another computer and download UBCD4Win
CD ISO, burn it and then boot your computer off of it and use the file recovery tools on it to scan for them.
EDIT: I should mention that depending on the size of the drive/partition this could take a very
long time - I've spent 4+ hours waiting for a scan of a drive before the software presented a list of files that could be recovered.
Oh yeah, and the obvious recovery method - restore from the backup you had