Halp! MBP shuts off as if power is pulled when playing gamed in Vista bootcamp

[mkor]

I use an older MBP from 2006 with a Radeon x1600 with updated drivers. Just about a year ago it ran just fine in bootcamp (last I was trying to play games on this thing). I was thinking it might be overheating but I don't know anything. I have the fans cranked all the way up and everything though. I really don't know what's going on. It just goes black with no warning, it doesn't hang, no blue screen, its like my power was just cut. It does the same with the battery in and out, if that matters.