The most popular disk cleaner by far is this one you will find on
as the description says
"Active@ KillDisk conforms to US Department of Defense clearing and sanitizing standard DoD 5220.22-M. The most secure Gutmann's data destruction method is also implemented. You can be sure that once you clean up with Active@ KillDisk, sensitive information is purged out forever.
It has had over 470,000 downloads with the next popular one has only had 31,690 which speeks for itself.
Can anyone advise the best software or process to clean out my old computer of my files, etc so that I can donate it without worry of someone getting my stuff? Thanks.