It seems to be completely random. It might happen while playing a game, or it might not. If you just leave the computer idle for a couple hours, it'll shut off on its own too. It's shut off in as little as about 20 minutes, but sometimes it takes hours. I just don't understand why the peripherals and everything would shut off, including the power and reset buttons on the front of the computer, but the fans would go full speed indefinitely until power gets disconnected. I don't understand how Windows could cause that, but I guess anything's worth a try.