It could be a faulty power supply not giving enough power to the vga. Is the crash occuring during games/hd videos? You can try to test the vga with FurMark and see the temperatures. High temperature can cause this problem - dust in the fan and/or dry heat sink paste . If Furmark doesn't show temperature you can use Everest. You can also check the "video memory stress test" to check the memory for defects.