computer crash with cd's

My friends computer keeps turning off when ever he inserts a cd into his disc drive. It just turns off as if someones cut the power. It usually happens within 30 seconds of inserting a cd, but at other times it can be compleatly random.

As far as i know his cd drive is fairly new and he has not had this problem before with it, but he has tried removing a stick of ram at a time to check for faulty ram, and he has disconnected one of the graphic cards he has... i seem to think it could be a faulty power supply? but i thought i wud ask the experts :-D