I thought if you really wanted to destroy it you take out the hard drive and drill a few holes through it.
If I was really worried about information being stolen from a drive I'd probably drill holes through it, then take it apart, then smash the pieces. Maybe rub a few magnets on the discs for good measure. There would probably be fire involved as well.
Overkill? Perhaps, but that's how I roll. 8)
In reality, since I'm a pack rat of sorts, I think I still have every drive I've ever owned...