Problem with my GPU

So I recently started playing a game with my friend after 6 months of not playing. as of now whenever I'm in game randomly my screen will freeze for about 15 seconds and then my PC will randomly restart. the card I'm using is a ATI Radeon 9250 PCI, I've updated all the drivers and ran the troubleshooter and the problem still occurs. I can play until I get into a part of the game where there is a lot going on around me, up until this point the game runs fine no problems with FPS or freezes and I cant seem to figure out what the problem is. Please help!
 
That video card is very minimal, and can you give us your computers specs and version of Windows?
 
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