Correct, you need speciality hardware to retrieve the very low remnant magnetic signal from the HD heads. Some small residue of the original data can exist even after some wiping cycles, but it gets almost impossible to recover it after just a few random overwrites. Check out the DoD standard for what they deem adequate. Some special services used to have an X marked on the back of their laptops, as an aiming point for you trusty 9mm, alledgedly
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