I used Ccleaner's free space wipe utility, and I have to wonder how Piriform can avoid the charge of false advertising. I set CCleaner to wipe the free space at 7 passes, took 2 days to complete. But Recova was able to not only "find", but "restore" many files...some of them having been deleted more than 3 months and two destructive OS format-and-reinstalls previous!
Somebody else discovered the same problem of failure to securely delete, and started a long discussion over at
http://www.wilderssecurity.com/archive/index.php/t-206024.html. When you load up that page, hit control-f and search for "one big file". Those who know what they are talking about simply throw their hands in the air concerning Windows. If you don't encrypt the entire drive or physicaly destroy it, data you think you have securely wiped will still remain.
An academic paper says many claims of secure software deletion by software manufacturers are bogus. See "Secure Deletion Myths" at "http://www.filesystems.org/docs/secdel/secdel.html
The academics appear to agree that there are only three possible ways to ensure data security in Windows: 1) encrypt the entire hard drive (PGP or Truecrypt), or 2) use a virtual drive (i.e., so that any changes you make or data you add will disappear when you turn the virtual disc off, or 3) physical destruction of the disc. Acronis has the virtual disc ability with its "Try and Decide" feature. When it is on, you can make changes by installing programs or copying files from other media to your computer, but when you turn it off, all these changes disappear and the computer reverts back to exactly the state it was in before you turned on virtual disc.
Nobody likes a conspiricy theory, but then again, it would behoove the government, concerning its objective to crack down on child porn and other illegal computer use, to ask manufacturers of "window washing" utilities to bypass certain windows files during cleaning, or to not actually wipe the free space, so that if law-enforcement can execute a search warrant on a suspect who has installed these programs to destroy evidence of his/her unlawful deeds, the chances will be increased that some incriminating data will remain. Ccleaner is not the only culprit. PurgeIE also claims to securely wipe data from the "recycle bin", yet after doing so, I was still able to recover it with Recova.