Try this program ASAP don't download or install anything till you do. You will risk overwriting the files if you do

http://www.download.com/Restoration/...ml?tag=lst-0-1

BTW this is for Windows. You don't specify which OS you use

If it doesn't work then have a look at this thread

http://www.gnutellaforums.com/showthread.php?t=49851