Recently our Dell Optiplex 330 experienced some pretty severe virus attacks that render the computer useless. The user had disabled the installed protect advising that it slowed his performance and would not let him install cute little things from his favorite social network. The machine was so hosed it was determined the best course of action was to reformat the drive and basically start over. The problem is this unit was sold to us by Dell with a license for Windows Vista Business which we request it be down graded to XP service pack 3. Each time we attempt to reinstall windows xp from teh provided original disc we get the famous blue screen advising there is a problem with the hard drive, etc. How can we reinstall the our favorite XP? The unit has a SATA hard drive. Any assistance would be greatly appreciated.