[l2ridehd]

You need to physically destroy the disk. Cut it in half with a carbide metal saw, then smash those halves with a sledge hammer. Drops those smashed halves in a bucket and dump some type of acid on them. Then bury the remainder in a deep dark hole. Destroying the surface so it can never spin or be removed somewhat intact is the only solution.

There is no program that can over write a drive so it can never be read. They can make it harder and more expensive, magnets can force you to unscramble, but the original data can be recovered with enough time and money.

Now depending on what you have on those drives will determine what method you use. I cut mine in half, smash with a sledge, then throw the pieces in the trash 1/3 a week for three weeks. Not fool proof, but very safe.