Card is Sapphire branded
When I play a video game (skyrim, portal 2, tf2, even non steam games) my computer will run for about 35-50 minutes and then it will suddenly shut down and I have to reboot to turn it back on. I've had this problem on a previous computer and was unable to ever fix it. I ended up throwing that computer out and that was around 3-4 years ago. I'd like to keep this pc as it's the only one I have.
I'm suspecting it may be a heating issue or there is a lot of dust or maybe the card may be fried.