Dead Motherboard?

[LuckyTxGuy]

Ok, time for me to ask a question.

I've got a customer/friend's E-machine desktop here and it's a freebie job so I don't want to spend forever fixing it. The friend is older and knows little about computers. They said one evening when they booted it the keyboard wouldn't work and everything seemed really really sluggish. Then the mouse wouldn't work, but they got XP shutdown. (pulled the plug?) Anyway, next day it's dead. Nada. Won't power on at all.

Enter: Me. I bring it to my office plug in a power cord and hear a quiet but high pitched squeal from the PSU and the machine is dead. No lights, no fans, NOTHING. I assume it's a bad PSU. My PSU tester shows that the PSU is putting out too much power, it doesn't give me an exact reading but the code translates to too much power. I put in a brand new working PSU thinking that is it and to my surprise, nothing. Dead.

Then I'm thinking it's the power switch. I used my meter to determine the switch is in fact working. Odd. This thing is just flat dead.

Any thoughts? I've almost convinced myself it has to be the motherboard. What do ya'll think?