And contrary to your belief, it COULD have something to do with the storms. I assume you use an ethernet cable and card to connect to the internet, and if that's the case lightning could very possibly have traveled through that and fried your PC. Yep, you don't need to have it plugged in to get it fried. I've dealt with many computers that were fried via the modem or ethernet connection.
Actually that's what came to my mind, too.
I was going to say temporarily short the CMOS setting on the motherboard, but probably not in this situation.
Yeah I don't think that messing with the CMOS would do any good.

My advice, provided Stephen doesn't want to attempt to tackle the inside of the PC himself, would be to take it to a place like FireDog or Geek Squad, at Circuit City or BEst Buy, respectively.