A PSU won't fry your board just by flipping a switch... there's no way in hell.
Maybe 10 years ago before power supplies didn't have detection (or did they...?) but definitely not now. The best way is to just put the shit in a microwave, like Sov suggested magnets, but only if you have scientific grade magnets... it takes a big magnet to fry a HDD.
Well the washing machine/dryer outside of my friend's room succeeded in cooking his power supply three times I believe. He had to buy a new one each time.
Dude, Jesus was so goddamned black it's not even funny. He met my great-great etc. etc. Granddaddy once, and he said, "Niqqa gimme yo do' befo' I done bust an arrowhead in yo' black ass. " I'm not even joking. A little known fact about Jesus Christ is, he not only invented Christianity, he also invented the Bloods. In case you don't know they are in an all-out war with the Crips.