I moved folders offline and deleted them using CTL/Delete key. Free space shows initially, but then does not after a little work is done offline. Did a search on C: for folders, they are gone and Recycle bin is empty. Disk is full except for like 150mb.
I then moved and deleted other files(music and Pictures) which then showed 1.5gb free, did a little work in tax pgm and then free space is gone again.
Offline folders are usually used in a domain to sync part of a server drive to a local drive so when you are "offline" aka out of the office thoes files are available, and will sync any changes when you get back.
If you have asked windows to sync a large server folder it will continue to eat up any space you free trying to do so.
From an explorer window select tools then Offline files to view your settings and any offline files.
Alternatively check out Treesize, it is a great tool for Hard drive cleanup