Hard Drive Eraser

A large company I work for is liquidating their supply of old computers: some will be auctioned, some will be donated to worthy causes. Recycling is great, but you don't want to recycle your sensitive data along with the hardware. Before you let that drive out of your house, zap it (for free) with DBAN: Darik's Boot And Nuke.

DBAN works on both Windows and Linux boxes, and because it’s GPL'd software, it's now also available for PowerPC-based Macs, thanks to a kind contributor. (Mac OS X has its own Disk Utility.) DBAN is great because you run it from a boot floppy or boot CD. Linux users should also look at shred, bundled with the GNU fileutils package and thus available in most Linux distributions. Shred can destroy disks and also be used to permanently delete individual files. (To scrub individual files off of a Windows machine, one of the best options is the wipe command that comes with the PGP encryption utility.)

With great power comes great responsibility, though. You should label your DBAN floppy carefully, and store it somewhere where no one will accidentally pop it into a machine and reboot.