Ironically, the best way to "clean" an old hard-drive is a rather old, but effective method.
1) Remove hard drive from the computer - make sure it is unplugged and you are grounded properly
2) Place the hard drive on your workbench, driveway, floor or other sturdy, non-porous solid surface
3) Place your safety goggles and face shield on. Also make sure that your extremeties are also well protected
4) Lift sledgehammer
5) Bring sledgehammer firmly down on drive case, smashing it
6) Repeat steps 4 & 5 as needed
Cleaning attempts could still be overcome by expect data recoverers, however, if the drive is destroyed it cannot be recovered.
