You wouldn't need to damage a hard drive to accomplish this.

Erasure of your hard drive only targets fat tables, and directories. The data is still there on the hard drive, all a hacker has to do is read the actual physical sectors (which there are utilities that can do this very easily).

What you need to do is wipe out the physical sectors themselves by overwriting them with zero's. In fact, I used to remember such a program by Norton called 'Wipeinfo' which would do this for you. I haven't seen that utility in years, wonder if it's still being sold?