Believe me, I have been there.
The best solution would be to sell it while it's working. Sure it may fetch u as little as a hundred bucks, but u won't get even that if u break it.
But ofcourse, there's the fun side of life too. I mean, when will u next get a chance to blow a motherboard
I suggest u place metal pieces on the mobo contacts as if they were battleships and the mobo is a battleship board. Try your luck (or the mobo's horror) by turning on the power. Try different positions each time and try it till u hear a pop. Kinda like playing battleship + Russian roulette with ur mobo
If u can, send us a photo. Don't bother if u haven't managed to destroy less than 10% of the mobo surface, though.