I downloaded real audio files to clip and need to remove them

When I first got my Sansa Clip I opened my music and dropped my songs from real player into the clip. They were the wrong format (real audio) but I did it anyway. I have since converted the songs correctly and added them, but the clip shows that I have used twice as much memory as I should have. How do I remove the wrong files? They don’t show up in any folder. Thanks 

Could this be it?  Files transferred when connected in MSC mode only show when connected in that mode; same as to MTP mode.

You always could reformat via the Clip’s settings as well (altho that will delete all the Clip files).