Games Crashing.

[mrsmiles20]

I just upgraded my GPU from a 4870 to a HIS 2gb 6950. I performed a clean install of windows 7 and installed the newest GFX driver updates(11.6) which I got from the AMD/ATI website. Games like Civilization 5, and normal computing and web surfing are fine. However, when I try to run high end 3D games like The Witcher 2 and Fear 3, the game will randomly crash after 4-10 mins of gameplay, often my computer will restart itself afterwords, though sometimes it will just sit at a blue screen. Occasionally it will bring me to a BSOD, but not always. I have done memory tests, though I did not think that was the problem as I just got the new GFX card. I uninstalled the drivers in safe mode with driver sweeper, and installed 11.5 instead to see if that worked any better. No dice. Still crashing. Windows 7 is all up to date, except for a failed 6*** series GFX driver update, which I assumed did not work since I already have drivers installed.
MY computer specs:
GPU: HIS 2gb 6950
CPU: AMD 955 Black Ed.
Ram: 6gb 10666 DDR 3
MOBO: Asus M4A77TD PRO AM3 DDR3 AMD 770
HD: Two 1tb 7200rpm Seagates(Raid 0)
OS: Windows 7 Home Premium
Power supply: 600W

 

[mrsmiles20]

Anyone? Is this in the wrong forum?