Destroyed Hard Drive
After multiple secure erasure passes, nothing gives that extra bit of confidence that your old data is completely unrecoverable quite like physically destroying the entire hard drive.
(This is the IBM-brand OEM hard drive that I pulled from my old Apple PowerBook 5300c. iFixit has a photo of one of these drives pre-disassembly: guide-images.ifixit.net/igi/gauSSVRmRZCPPClE.huge)
Destroyed Hard Drive
After multiple secure erasure passes, nothing gives that extra bit of confidence that your old data is completely unrecoverable quite like physically destroying the entire hard drive.
(This is the IBM-brand OEM hard drive that I pulled from my old Apple PowerBook 5300c. iFixit has a photo of one of these drives pre-disassembly: guide-images.ifixit.net/igi/gauSSVRmRZCPPClE.huge)