Huge Problem-Random Crashes

When I play a game, sometimes it will randomly crash. Not only will it crash, but my entire computer will turn off. This isn't a heat issue, as this is the only game that this happens with. If it is, it means the game is somehow screwing with my cooling. If it isn't, then Stardock needs to look at this issue. Its not cool, and it happens really often, sometimes once every single game, especially online.