I would recommend you:
-Install HWMonitor and prime95 to see if your processor isn't overheating.
-Verify if your ram sticks are clean and tightly secured onto the motherboard, then test it with Memtest86 or something else.
-Test your hard drive for bad sectors.
-Try your video card with any stress test.
-Reinstall your mother board, video card, etc, drivers.
-Test different video card drivers.
-If nothing accuses hardware errors, make a fresh windows install.