do you have a surge powerbar to protect that system ? if not then the overvolt could have damage also the board .
You mean between the wall outlet and the computer? Yes. The "overvolt" or rather the lights flickering I thought was from the computer, not the house.
Do you have a multi-meter to test the output voltages on the PSU? You can get one for about $12 at Radio Shack.
I'm home for the holidays and the computer is actually my sister's computer. I don't have my usual set of tools, but I'll see what my dad has.
If I assume the power supply is good (or I find out by hooking up a fan and using a multimeter), do you guys know of an easy way to determine if I should replace the motherboard or the video card or both? I don't think it could be any other part in the system, could it, especially since I'm not getting any system beeps?