Lots of things can give you a generic eror like this. Most likely it's a bad or corrupted hard drive.
You can try - reinstall operating system, but you will lose your data.
-try a recovery program, I always recommend GRC*|*SpinRite 5.0 to 6.0**
-If you have Vista or XP you can try to repair the boot sector. Vista has a repair button, XP - search google for fixmbr and fixboot for instructions.
-Put the drive in another system and try to read and copy your data from that sytems OS

There are a few options assuming it's a hard drive issue, not a cable or other hardware issue.