|Test the hard drive with the manufacturer's diagnostic software. The links are here: http://www.tacktech.com/display.cfm...|
You will need to use the DOS version of the diagnostic software so that you can make a bootable CD with it. Then boot your faulty PC from that CD and the drive testing program will open.
If the test shows that you hard drive has failed or has errors that can't be repaired, you will have to fit a new hard drive.