Despite what a lot of people have been telling you, the problem you describe is (98% of the time) your power supply crow barring. Not much you can do about it but replace the power supply. They aren't that expensive.
I agree with the gut-consensus - power supply. Go to CompUSA or some equivalent and get a 400W or better - worst case, you have a spare IF that wasn't the problem - but someday you'll need it.