Before yoy futz around with chkdsk /r, or fixmbr you should determine in the drive is even salvagable. Thus you should google Ultimate Boot CD. Burn it to a disc. Boot to the disc. Then run the Hitachi Hard Drive Fitness Test, or a test the corresponds with the manufacturer of your hard drive.

If it passes, boot to the XP cd (asuming you are on XP) and run chkdsk /r from the repair console. More on that later. Right now, figure out if the drive is good or your are just wasting your time with the command line fixes.