will I wipe out files if I run the "wipe free space" option or will this just do a more thorough job of cleaning?
It's my understanding that if something is written to a drive - then deleted - it still remains on the drive until that space is overwritten. All a wipe does is remove what was once there completely - writing the drive to 0's. I may be wrong, but I'm sure someone will let us both know.
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EDIT: Decided to do it for you: http://docs.piriform.com/ccleaner/using-ccleaner/wiping-free-disk-space
will I wipe out files if I run the "wipe free space" option or will this just do a more thorough job of cleaning?
No you wont loose any files. You dont need to run wfs unless you are selling your computer and worried about sensative data being recovered.