Data recovery software free and decent : http://www.cgsecurity.org/wiki/PhotoRec
Some help info : http://support.microsoft.com/kb/823439
You can try this also :
You can boot from your Windows 7 DVD, work your way through the "repair" menus and select Command Prompt.
Once your running under the command prompt (black screen with white letters), type
chkdsk C: /r
and hit enter.
It will take some time so be patient.