Windows Update is just general fixes and security fixes for Windows. I doubt there would be a fix (if any) that somehow fixes the problem.
It could be a power supply problem. Or it could be a hardware problem - your MOB might have a fault going on. In fact, the inside of your computer might be getting too hot. Feel the tower and see if it feels really hot or something.
If you want, you can always take the PC to the shop.
Chris