Today when I got out of bed, my APC Back-UPS XS 900 was beeping a continuous beep, and the "Overload" light was on, and both pc's were off. I turned the APC off, and unplugged one pc from the APC. Then I turned the APC back on and re-plugged in the other pc I had just unplugged, and I heard a loud 'POP' from the pc, and the APC light went to "Overload" again. Everything connected to the APC (both pc's & monitors, Comcast Modem, Linksys Router) turned off. I saw sparks and smoke come out of the power supply of the pc that I first unplugged. I unplugged that pc from the APC again and turned everything off. I wasnt sure if smoke also came out of the APC or not since that electrical smoke is really strong and it is hard to tell what piece of equipment is smoking. So I took apart the pc that popped and the pwr supply smells like the smoke. I am pretty sure that pwr supply is shot, so I will buy a replacement, but do I need to test any of the other internal parts of that pc (system board, peripherals, the Router) to see if they got hit with something from the bad pwr supply?