I used CCleaner and found out that you have to delete firefox and chrome since they act like a cover over the areas of the hard drive that you want cleaned. If you don't delete them then lots of files won't be overwritten. You may have to delete other programs too. I found this out since I used Recuva and the files I wanted permanently erased were still there. Once firefox and chrome were removed from my PC I ran CCleaner a second time and then I used Recuva a second time and the files were gone.
Then I used a program called disk investigator and I found out that some files were still recoverable by using the internet links found in the disk clusters on the hard drive. You just have to know what word to search for and you will get list and those list will contain internet links and other sensitive information. If you search for "downloader, jpg, .com, etc..." it will pull up a lot of what you have been doing on your pc even after running CCleaner multiple times. Is their any way to permanent clean the hard drive so that even disk investigator can't recover the information?