My 2 year old Gateway computer shutdown today; when I rebooted, it said it shut down because of a thermal event. I opened it up and everything seemed ok. I couldn't find any hotspots. I called Gateway, and they said I could have it fixed for $389, or buy a new one for $499. What causes a "thermal event?" Do I need a bigger fan, another fan, is the mother board overheating, is it the drive, the cards??? How do I find out? And can I add a fan and still use this pc?