There are a ton of reasons why you might want to physically destroy a hard drive rather than use disk wiping software:higher confidence that the data is destroyed, a recourse if your drive has failed and no longer accessible, and sheer fun.
If the thermite method and other extreme physical disposal methods aren't for you, dismantling the drive to get to the platters is an alternative method.
The main process involves removing the screws around the outside of the drive, pulling out the screws holding the electronics, and then popping the cover off.
After removing the magnets, you can get to the platters, the heart of your hard drive.
First run the magnets over the platters to degauss them. Because that's not a guarantee that the data is unrecoverable, you should then physically destroy the platters, bend them or break them with a hammer or saw them into pieces.
And that will be the end of those discs and the data on them.
The video below shows how Google use a disk crushers and the destruction of old hard drives to prevent leakage of customer data.
