erasure methods

You don't need fancy degaussers, just a set of Torx screwdrivers. Open the case (usually T9 screws, IIRC, a few are hidden under labels) and remove the platters from the spindle. Take one of the powerful magnets that control the motion of the armature and wipe it across the platters. That will re-align the magnetic fields nicely. Then give it a good scrubbing with #4 steel wool, which will do horrors to the platter surfaces.

Incidentally, the platters are extremely flat and nearly perfect mirrors, which makes them useful in optics experiments. I've bounced lasers off them and been unable to see where the beam hits the surface - there's no light scattering.