Erase the Hard Drive.

Deleting a file from a computer is only a concept not a reality. A file is not deleted; only its name is erased from a file database. Beyond the obvious deletion functions, you start getting into secure deletion, the act of clearing, overwriting, wiping or "scrubbing" the data once or many times with a string of 1s and 0s. In the middle of the spectrum are devices, such as degaussers, that purge data from a variety of media.