Via Digg I found a site that has an excellent compendium of tools that can aid you in rendering a computer difficult or impossible to recover useful forensic evidence from. The tools listed on this site are intended to be used for educational purposes and in defining problems with existing forensic software and methods so that more effective software and methods can be developed.
Many of these tools stem from the fact that most OS’s don’t actually remove data when you delete a file they simply flag that area as available to the OS for writing. So even if you remove a file the data is still on your hard-drive. Many tools like fwipe or srm not only unlink the file but write over it with null or random bits. This effectively destroys the data.
Check out the list of tools over at www.networkintrusion.co.uk