So I've had my Pc for about 6 years its a prebuilt I've never taken out any parts or messed with anything since i got it in the mail its been a beast and everything ran awesome all this time with no problems playing any game on it. But last week i needed to use my printer and long story short, The pc was already running and i plugged the usb part of the printer in the motherboard on the back of the pc where i plug all kinds of other stuff just fine, then i plugged the power chord of the printer into a outlet and boom sparks flew and the computer shut off and now it wont turn back on whatsoever. I took it to a shop cause I'm not a crazy computer wizard kinda guy but they told me the motherboard was fried but all my other components are safe and still working only thing they didnt check was the power supply for whatever reason. Can anyone shed some light on why this happened so i can prevent it from happening again? or maybe salvage or re test the motherboard to make sure the people at this repair shop are telling the truth?