Hard Drive Eraser
Wiping the data from your hard drive isn't complicated or expensive, but it involves more than simply deleting files and emptying the trash. Those steps remove the record of your file, but the sectors full of data remain where they were. No operating system wants to make you wait the multiple hours that a true wipe requires.
For most people, effectively wiping data involves firing up a free utility Darik's Boot and Nuke or Hard Drive Eraser. DBAN, which works via a boot disc or floppy, securely wipes every drive attached to the PC. Hard Drive Eraser runs under Windows and lets you selectively wipe individual partitions and drives. Both use the National Industrial Security Program's DoD 5220-220-M "data sanitization" protocol.
--Jon L. Jacobi