I've had this pc about 4 years. I used it fine one day, but now (1.5 days later) it will not start up at all. There is no sound, no fan, no lights. There have been no storms, no suges that I am aware of. I tried unplugging the power cord for over 5 minutes and holding the start button in for ~30 seconds with no luck. I am inclined to think it is the power supply. Suggestions?

Thanks!