My Father in laws laptop has started shutting about 30 seconds after it boots up and then becomes unresponsive for about 2 hours. It's plugged in so I don't think it's an issue with the battery so I'm guessing it's overheating. Does anyone have any idea what else it could be? It boots up fine and is OK for the 30 seconds or so it is on but once it shuts down, that's it. It's an Windows 7 HP laptop if that's of relevance.