Today the subject of deleting hard drives was raised in the #snort-gui IRC channel. jrk and geek00L mentioned using Darik's Boot and Nuke (DBAN), an open source (GPL) "self-contained boot floppy that securely wipes the hard disks of most computers."
I found DBAN very easy to use. It boasts some impressive features too.
When you boot from the floppy image or CD-ROM .iso you see this screen.
The About screen offers warnings and caveats.
I like the ability to boot using one of the available deletion methods.
I simply hit [enter], which started DBAN in interactive mode. Here you can set parameters for wiping the drive.
In the future I plan to carry a DBAN floppy with me to wipe hard drives prior to installing my own NSM software.