Recuva restores files after CCleaner run. Why?

I have run CCleaner several times on my Win XP Hewlett Packard desktop.

I wanted to make sure deleted files were truly gone, so I ran Recuva. LOTS of files were restored to a plugin hard drive.

Why?

How do I make sure that deleted files are gone?

Can I delete them from the plugin hard drive (using CCleaner) and they'll be gone forever, or are they still on the C drive of my desktop?

Thanks for any help in understanding how to use these 2 programs.

Recuva is just doing what it's supposed to do...recover deleted files. To truly delete them, you need a file shredder program.

If you use a secure file deletion (you can choose that in CCleaner's settings), it shouldn't be able to restore anything. Or only file names.

Just to expand on Aethec's advice, have a read of the CCleaner docs on Secure Deletion, and I would suggest choosing a "Simple Overwrite", which is sufficient.

http://docs.piriform.com/ccleaner/ccleaner-settings/changing-ccleaner-settings