[GraemeJ]

The files only exist once, the different apps just have pointers to the individual file locations. If you delete the file, then nothing will see them. If you don't want a particular app to see the files, you need to delete the pointers, or the app (if you don't need it) - not the files.

Actually, the pointers take up very little storage space and it might well be advantageous to have the files viewable by other apps than MS. Personally, I wouldn't bother with trying to change this.