SAPPHIRE HD 7970OC UNABLE TO PLAY ANY GAMES EVEN ON LOW QUALITY

Hi Bros and sister ,

Im not a hater in AMD i heard alot of good stuff on their product before i bought it but i encounter such problem which i had no clue i tried google and find everything i could but still cant find the problem im getting kind of impatient and dissapointed with the product

i bought my computer yesterday but after fixing the computer parts its seem wierd . After installing window 7 OS sometime like 50% when i startup my computer it show window are starting up it hangs there with the win7 logo not moving . the 2nd MAJOR problem is after i update all the drivers when i go to skyrim it start the game perfectly but after less than a min , My Monitor turn black with a message saying no signal when i can still hear the game sound than suddenly i hear the sound like GRRRRR hanging sound and the computer restart, Sometime grey screen with white strip , or it closes skyrim and a message popup saying something like display driver is not responding but was recoverd . <EVEN ON LOW SETTING> Is there something wrong with my computer built ? GPU SapphireHD 7970 OC MB ASRock Fm2a75m-DGS PSU seasonic M12 bronze with 650W . Does anyone know what is the possible problem ? This is so depressing I somewhat felt like injustice like i got scamed from seller without know what cause such problem