Laptop HDD fried my mobo

Well Houston we have a problem! I got a set of laptop HDDs from a friend yestreday with the intentions of running them in a low power RAID............ well I decided to connect one to one machine and the other to another machine............... POOOOOOF one of them fried a Zotac.......... for this project: http://www.tomshardware.com/forum/ [...] w=0&nojs=0
I dont get it, A laptop HDD fried MY BOARD ........ huh? I know thats what it is because it fied my usb HDD drive adapter as well. I also have changed out the board with another one I had laying around, used all the hardware from the first one, except the board of course and bingo it worked. Im up and running again. I tested the other board on my test bench and it wont post at all no matter what.

Anyone with any idea why this would happen would be greatly appreciated!

Positive! Ive checked all of them on another drive. Then I even checked the bad HDD on a BS p4 build, just to watch and see if the board would die.... it did! Attack of the KIller HDD

no it was a Seagate sata 2.5" 5400.2 momentus. It was connected correctly to both connectors while the computer was turned off with the power cord disconnected.