Every few hours or so my computer will freeze and displays distorted image of what I was just looking at. This usually happens when I'm browsing the web on Firefox. I don't think this is an overheating problem because the CPU, GPU, Onboard Graphics etc. all seem to be at regular temperature when this occurs. I have to force shutdown the computer and reboot to use it again. As precaution I bought some new thermal paste for the CPU to replace the old dried up. I have purchased a new IDE video card as well.
Here is some links with more information: