I am working on a friend's Window's XP service pack 3 computer. I am trying to clean it of suspected viruses. When I attempt to run an antivirus program or a virus cleaner I recieved messages that the program virus data could not be updated or the program encountered a problem. I have unsuccessfully tried to run Stinger, MS Malicious Software, Security Essentials, Avast and RemoveIT Pro v4--SE. I have attached examples of the messages I recieve. I have also tried all of the above in Safe Mode with the same result. Now, rarely, as in the case of running Malicious Software Removal, it did run for 26 minutes and before it finished ... the computer shut down and rebooted. It shuts down and reboots frequently for no obvious reason.