Disk Wiper best is so say Peter Gutmann
http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html
Secure Deletion of Data from Magnetic and Solid-State Memory
Peter Gutmann Department of Computer Science University of Auckland
http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html#recommendations
allso ccleaner for free space & eraser
dban will kill all no get date back
Is the Gutmann method the best method?
No. see or take link to Peter Gutmann
http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html
iso burn to CD / DVD
http://sourceforge.net/projects/dban/files/dban/dban-2.2.6/dban-2.2.6_i586.iso/download