[RaNgeR]

We bought a new p4 3.0 a few months ago, and it has worked like a charm. Lately though my parents have been complaining its slow, so I went on their names to take a look. They used IE and programs like that, so I thought I would run antivir, adaware, and SB Search and Destroy. When I run it a NT Authority Logout commences and restarts the computer. I cant figure out how to stop it...It weird, everything works fine on my username and everything is extremely fast. Can anyone tell me what to do?

Well, now NT Authority/System shutdown starts when I run any kind of anti virus program. EDIT