New computer running windows 8 keeps freezing during somewhat video-card intensi

Hello,
I just built a new computer: Intel i5-3570k, Sapphire Radeon HD7850 gpu, Asus Z77 extreme4 mobo, 8gb of ram. I installed windows 8 on it, and the first time it froze I was on google maps street view. I tried to click over to another tab and the tab highlighted but then froze, although I was still able to move the mouse. I then tried to open task manager and it froze, including mouse, on the ctrl+alt+del screen. Waited 15 mins and nothing, so I shut it down.

Next time happened after using Unigine Heaven. I Xed out and then tried to open my browser and it froze. Waited 15 mins and again nothing. Clicked around and mouse froze. Shut down.

Just happened again while playing Skyrim. I had probably been playing 45 min-1 hr, and then it froze. Waited and nothing, shut down.

Is there a chance this is a windows 8 problem, or does it probably have more to do with my computer? My video card seems to be running fine. Thanks for any and all advice!