Yesterday, after the internet went out for whatever reason, I came back to find my PC off. Naturally, I pressed the power button, and nothing powered on. Problem.

So, I thought it might be the power supply. I don't have considerable experience, but I have a case fan with LEDs. When I just plugged in the PC, and hit the power button, the LED lit up briefly with nothing else. So, I took in the power supply to have it tested, and it turned out that it was live. I took it down to a barebones system, after reinstalling the power supply, and it still did not POST. So, I switched the RAM sticks, trying each of my sticks seperately, and shorted the power switch, without having any result. After this, I reset the CMOS, without having any luck.

Luckily, I had a second motherboard ready. So, I put that one in there, and placed all of the components in. And, as luck may have it, it POSTed. Unfortunately, I was unable to get into Windows because of significant changes to my hardware.

My actual question is relatively simple. Based on what I have done, does it seem as if the first motherboard is the problem?

I am reasonably sure of this, but due to many stores' refund policy, I want to make sure about it, so as not to waste my money on something I don't need.

My barebones system specs are as follows:

PC2700 DDR333Mhz RAM single stick
2.4 GHz Intel Celeron Processor
FSP200-60ATV Power Supply
GA-8S661FXM motherboard

Thanks in advance. This problem bothered me for most of today and yesterday.

if it powers down it was very possibly a virus. now with your new setup all you need is to setup a fresh install of Windows. The first motherboard you had may or may not have been bad, it would require much further testing.

You said the Internet went off for some reason. Did you have a power outage or storm of some sort in your area? If you had some sort of a power problem that could be the cause of the problem and it may have damaged the motherboard. Did you use the same processor in both motherboards? If your system would not power on at all, then I doubt a virus that caused that specific problem.