getridofit

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.