I use this software to wipe hard drives of all data.
This is a slightly controversial area but as best I can tell Darik’s Boot And Nuke Disk Shredder seems to be well regarded.
Darik’s Boot and Nuke (“DBAN”) is a self-contained boot disk that securely wipes the hard disks of most computers. DBAN will automatically and completely delete the contents of any hard disk that it can detect, which makes it an appropriate utility for bulk or emergency data destruction.
DBAN is a means of ensuring due diligence in computer recycling, a way of preventing identity theft if you want to sell a computer, and a good way to totally clean a Microsoft Windows installation of viruses and spyware. DBAN prevents or thoroughly hinders all known techniques of hard disk forensic analysis.
The development and support of the DBAN software project is funded in part by GEEP International. GEEP is the largest, the most efficient, and the most environmentally conscientious consumer electronics recycling company in North America.
Its easy to use, download the iso image, burn it to CD, reboot and wipe the partitions of your choice – mind you it takes an awful long time per disk ( > 12 hrs for a 60Gb laptop drive )
dropped from 10/10 to 7/10 for time taken to shred a disk