Weird stuff going on lately. I've run Hijack This, SpyBot, and Panda anti-virus, all of which have found nothing.
I first noticed that windows would close on their own. After some trial-and-error, this seems to occur when Yahoo Messenger or Trillian are open. Notepad, Calculator, MSPaint, and a few other things like some software installers just show up briefly and then close whenever I move my mouse. Command Prompt works fine.
When playing Team Fortress 2, Windows XP (5.1, Service Pack 3) would just restart randomly. It happened once when I chose to exit the game and once when the next map was loading.
Is this just possibly a corrupt Windows install, or something more malicious?