Many folks assume that if they format their hard drive a few times, their data is going to go away. That’s not the case though. You need to crush your hard drive and degauss it. These 2 degaussing wands can help with your cause:
Proton 1100 Degaussing Wand: a lightweight and portable device that erases information from disk drives and other magnetic media.
Datastroyer 102-DG Disk Eraser: a degaussing device evaluated by NSA and proven to meet the applicable NSA/CSS performance requirements. It is portable and helps keep your data protected.
These degaussing devices are not cheap but help delete your data. They are easy to move around though.