It sounds like it could be a power supply issue, as in the computer not getting enough power. How old is the computer? Is he using a quality powerbar?
Dis tells ya it isn't an "OS" problem. Anything that uses AGP4x (I'm assuming this is the class you are in) needs AT LEAST 300 watts of continuous clean power with one HD and one CD. All it takes with a 250 watt is a few things starting at once and strange things start happening, similar to a virus. I have 400w power supplies in both my main boxes and a 300 in one that isn't even AGP, because I have had major problems twice with power supplys being insufficient.it does this in Win XP Win ME and Dos