It's not just Team Fortress 2, either. I tried playing several other somewhat high-demand games, with identical results. Today, it even crashed while I was downloading a few torrents. However, a few days ago, I decided to try Team Fortress 2 again. I got on, and played for nearly an hour without problems. Then, a message popped up warning about low battery. My charger cable had come unplugged (I keep my laptop plugged in almost constantly (bad for the battery life, I know, but I nearly never use it away from my desk anyway). I plugged it back in, went back to playing, and crashed within two minutes. I honestly have no idea wtf to do. I have never messed around with overclocking, or any kind of power-related settings.
Thank you for any advice you may be able to offer. The below image was not taken by me, but it shows roughly the same problem I am having.