Well, I just switched back to Windows from running Linux for a couple months. Keeping WoW working in Linux was driving me crazy, and I finally gave up.
I'm using a PNY AGP 6600GT that I got around Christmas last year. I've liked the card a lot so far, but ever since I switched back to Windows, I've been having problems.
My computer restarts itself quite often while playing games. In WoW it usually takes a few hours, where as in the Starwars Battlefront II beta and Serious Sam II it can take only 20 minutes or it can last an hour or two.
I'm using the 78.01 drivers. The system is fine if I'm not running games - its only 3d accelerated applications that seem to be giving me this issue.