Brother's computer keeps crashing

Hello, I'm Corbin, and I'm new to these forums. Anyway, my brother asked me to fix his computer for him, and I'm kind of stuck. What happens is the computer freezes completely, the mouse won't move, nothing moves, if sound is playing, it suddenly stops and distorts over and over. I get no error report, not even when I restart the computer. I checked out the event viewer, It has a bunch of reports that say something about the power kernel and the computer suddenly turning off. This has been going on since I had installed Windows 7 for him, and all his drivers are updated except for an audio controller I can't find anywhere. Please help, and thanks in advance.
-Corbinsor

Also, it happens when he's doing something like playing a game or browsing the internet, it never happens when it's just idle or installing something. I don't think it could be the audio controller, could it?
 
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