BSOD When Playing Games

I never get the bluescreen doing anything but playing games and it's not often but it happens about twice a week. It crashes and WhoCrashed or Bluescreen view always points to ntoskrnl.exe or ntkrnlmp.exe or hal.dll it's always two of those 3. Other than games it runs fine. I did all the memory tests for 3 days and tried the best I could re-seat stuff. It's an alienware so they have it all secured in a way that makes it difficult to get around, and the case weighs around 105 lbs or something crazy.