Pc freezeswhile doing any kind of stuff. I have checked all my hardware and the fault is in GPU. PC works fine without it. Tell me what should be done

Motherboard: Asus m4a88tm

CPU ( AMD/ x6 1055t / Not overclocked):

RAM ( Adata / 2*2gb 1333mhz):

Video Card ( XFX / HD5770 / Not overclocked, used for playing games like BF3, MW3, BURP3, GTA4 maya, photoshop, lightroom and other normal stuff ):

PSU (Corsair vx550 watt ):

Monitor ( Samsung / sync master 2233 / DVI):

Hard drives: 1, 500gb segate 5200rpm

Optical Drives:1, LG dvd rw

Additional PCI cards:none

Number of fans present: one extra fan on chasis

Operating System : Win 7 ultimate 64bit

Video Card Drivers in Use ( and tried ): Catalyst 12.1 currently, tried 9.8-12.1

Motherboard Drivers Used: Stock drivers

Apps/Games causing issues ( and if they've been patched ): Every game and software like windows phone devlopment kit.

All major components check 100% after thorough testing ( eg. Memory & Memtest86 ): All tested, no errors

System clean of viruses / spyware etc:

Other things tried: hardware acceleration stop, changing fan speed of gpu through AMD overdrive, RMA the card.

I created a forum already but i wasnt able to post on at due to some login errors.