Paleotech Formatting. When it absolutely, positively has to be made unrecoverable…
A hard drive used by one of our financial gurus at work died. A recovery service was able to get most or all of the data out, and I was asked to handle the warranty claim for a new hard drive. We had purchased the “no-HD-return” option on the warranty, and Dell did a nice job getting us a good replacement drive the next day — but we still needed to make sure the old drive couldn’t be read by nefarious evildoers (should they decide to go Dumpster-diving and have a cleanroom).
I vaguely remembered reading that one suggested Best Practice for such a situation involved a drill press — which we just so happened to have available in the lab.
I dare say the data has done left the building.
http://www.noob.us/miscellaneous/hard-drive-shredder-in-action/