Sansa Clip+ MP3-Player >> "Not enough space for music DB. Please free 90MB."

I recently had this issue but maybe because I use Linux I was still able to mount the Clip and delete the excess files.  I’m not sure how Windows works but both Macs and Linux create a hidden folder .Trash-0000 where all your deleted files go so you can restore them.  This folder occupies space on your drive and must be deleted.