RonaldJosephCote, that doesnt have anything to do with this blackout
live chess virus? Causing screen blackout

It's hard to tell without being able to check it out but it sounds like a hardware problem to me. Make sure your drivers are up to date, especially the video drivers. It could be your video RAM is forgetting what is stored for some reason or another. Are you overclocking the machine? That can have weird effects if the RAM can't handle the higher clock rates. Maybe it's overheating due to dirt or a bad fan (or overclocking).
I agree with the others that said it doesn't sound like a virus. Do you have software that runs under your account and not your brother's? Maybe you have a program that doesn't play well with others and is overwriting your video RAM.
Unable to chat in What old account Galileo ??