Hmmmm...........powering on is a big issue......an initial power up may be all that is needed to kill the psu if it is "sick". Obvioulsy, unless you spilled a beer on the mobo the night before when it was powered down, "nothing is going to be damaged" but the initial power up is a big stress for a weakened system. If you have another psu laying around somewhere, swap it out and see what happens. If it has been a reliable puter and you don't mind spending a little time evaluating it, it's worth the effort. If you can afford to upgrade do it! Part it out and forget about it!