This is complete FUD. Where did you get this info? There is no reputable data recovery company who will claim to be able to recover data that has been overwritten.
The fact that you compare analog audio tapes to a computer HDD, and refer to recovering overwritten data as "unencrypting" it, should be a warning to anyone reading this thread that you have a limited grasp of the technology.
Instead of spreading misinformation, maybe you should concentrate on the more important question - whether or not CCleaner does overwrite all of the data it claims to.
Here are some links for you to think about, John:
http://www.nber.org/sys-admin/overwritten-data-guttman.html
http://www.h-online.com/news/Secure-deleti...-do-it--/112432
http://www.springerlink.com/content/408263ql11460147/
http://16systems.com/zero.php
http://sansforensics.wordpress.com/2009/01...ard-drive-data/
http://www.securityfocus.com/brief/888?ref=rss
