I am working on two different computers belonging to two different people... Each will shut itself off during a virus scan or if you just use it for awhile. One is a laptop (P-III 1.1GHz / 512MB), the other is a desktop (P-III / 256MB). Both have Windows XP and run fairly well except for this problem... It does not matter what kind of virus scan it is.. Norton Antivirus, Mcafee, Trend Micro... Online scanners etc... It seems like anything that scans the hard disk in Windows causes these computers to shut off. I have physically removed the drives and scanned them in a seperate system using Norton Antivirus 2004, Mcafee 7.1, Panda Antivirus and Tred Micro PC-Cillin, but no viruses have been detected. I have also run disk, memory, cpu and system diagnostics through both systems. Each computer certifiably perfect. Here's the information I have so far: - Both systems have Windows XP - Drives are error free - No viruses found - Passed standard & extended memory tests (memtest86) - Passed 5 hour burn-in stress tests (DOS environment) - Power management is disabled in software and BIOSes - 3rd party power management utilities are uninstalled - Usually shuts off within an hour (varies) - Latest updates etc... Installed. The laptop did not have SP-1, so I installed it. Made no difference. I've seen some weird things, but this has me stumped. Anyone experiencing this out there?