Data recovery software
First of all you need to check if the Hard Drive got corrupted or is it damaged.If it is a damaged one data recovery software will not help.Check if your Hard disk is bad
Run the command prompt (with administrator privileges in Vista) and input the following command:
chkdsk x: /f /r
where "x" is the drive letter you want to scan (start with c). It may tell you to restart before it can scan. If windows does not find bad sectors it will attempt to move the data to another location. If it finds bad sectors, then your hard drive is (obviously) bad .
and if it is just corrupted use Recuva