Self Destructing Drive

Okay I recently managed to get a few hard drives, what I really have been wanting to do is make a self dustructing drive. I have done some thinking about it, and I would perfef if the ammount of damage done was limited to the drive its self, so no gun powder or thermite. I was condering somthing like a electro mag that I could put inside the drive case to wipe the bastard.

So anyone have any suggestions?

Well, I'm not sure about this idea, but here goes...

How about develop some alternative destructive mechanism onto the hard disk itself using the function it already is capable of? What I mean is, why not develop a way to hack the write/read speed of the disk to spin at crazy -- CRAZY speeds and have the read/write tool to scratch the fuck out of the surface till it's unreadable?

You'd need some sort of an alternative power source to crank up the RPMs to cause damage, and then a switch on that power source.