It could be, or it could be the RAM. Like I said before, you should try and test your main hardware component by unplugging and removing any unecessary hardware and just leave the CPU,RAM and Video card. If this distortion occurs, trouble shoot the RAM first, if not then Video card.
If the problem don't occur when you have just the CPU,RAM and Video card on, then start adding 1 hardware at a time. Start with the Harddrive until the problem is produce.