There is a similar question on Serverfault: How do I destroy a hard disk? - I wrote one of the answers: :-)
If you are looking for standard procedures and reliable methods, you could read the Guidelines for Media Sanitization (PDF) of the National Institute of Standards and Technology.
For any given medium there a three basic methods:
- Physical Destruction
For hard drives they recommend:
Overwrite media by using agency-approved and validated overwriting technologies/methods/tools.
- Incinerate: incinerate hard disk drives by burning the hard disk drives in a licensed incinerator.
- Purge using Secure Erase. The Secure
Erase software can be downloaded from
the University of California, San
Diego (UCSD) CMRR site. Purge hard
disk drives by either purging the
hard disk drive in an
- NSA/CSS-approved automatic degausser
or by disassembling the hard disk
drive and purging the enclosed
platters with an NSA/CSS-approved
- Purge media by
using agency-approved and validated
Degaussing any current generation hard disk will render the drive permanently unusable.