There are differing opinions about how to do this. Some suggest simply yanking out your hard drive, slipping on a pair of goggles for safety, and then smashing it several times with a hammer [source: Lamb]. Others recommend more elaborate measures — drilling holes or pounding nails through the drive; throwing it in a fire; cooking it in a microwave oven; or soaking it in diluted hydrochloric or muriatic acid. That all sounds a bit fiendish and can be hazardous to your health as well (acid baths give off toxic fumes).
A comparatively safer method involves disassembling the drive, removing the platters, and then sanding or grinding their surfaces to make them unreadable. You may have to invest $20 or so in a special set of screwdriver bits to remove the small screws that hold the drive's case in place, though you could also try a large flat-head screwdriver to pry it off [source: O'Reilly].
If you're a fan of the TV series "Breaking Bad," you may have seen the episode in which the characters park a powerful magnet next to a police evidence room to destroy incriminating data on a drive. In real life, that process, called degaussing, probably wouldn't work unless you had a really, really powerful magnet and focused its field very precisely [source: Lynn].