You can erase a hardrive without destroying it (say you were selling it, or donating it). No software or computer erasure program can do it, however you can utterly obliterate any information or echos of information by erasing the drive with a magnetic bulk eraser, such as TV stations used to erase 1" and 2" reel to reel video tapes.
A degausser is what you're talking about.
There are software packages that will remove all traces of data from a hard drive as long as it is US Department of Defense 5220.22 M compliant, like KillDisk, for example.
Searching my way to perplexion