dragonfly224 wrote:
Smash it with a hammer, throw it in the fireplace when you have a fire going, etc etc etc.
Do wear eye-protection. Modern disk platters are made from glass or glass-like materials and will shatter.
A single zero-fill or random-fill using dd (
dd if=/dev/urandom of=/dev/sdb) or similar Linux utility will overwrite the drive in a way that no normal user can extract any meaningful data. If you are not the target of the FBI or someone with a lot of money and specialist equipment, then overwriting the data is effective.
A simple format, even a low-level format, may leave data (banking details, personal data) on the "free" area of the disk that can be recovered with testdisk, photorec or other tools.