My computer is eight years old. I've recently run a lot of anti virus software and found at least one virus, but my computer still runs slow and the hard drive makes a lot of noise. I ran the Windows Built In Error Checking. After running this I did not receive any notification of a problem; the testing screen simply went blank. Does that mean that the program did not find a fault with the HD? Do HD tests test the quality of the HD heads? My understanding of computers is very rudimentary. Any replies would be appreciated.