@TomCunningham
MB's "library" is -not- your music files. The term "library" within MB refers to the database that contains information about your collection such as playlists, podcasts, It does not refer to your music files.
Hold the SHIFT key down while opening MB. A window will appear showing you the libraries you have. You can highlight one and click "select" and it will open. If you want to delete a library simply make not of the path. Quit that window and open a file explorer and navigate to the path of the library you want to delete. Then delete that directory. Now hold the SHIFT key down and launch MB and when the window opens you'll see that the library is gone. Needless to say, but I'll say it anyway, if you delete the only library you have, you'll have to start all over with creating your playlists, etc. If you're nervous about doing this, copy the entire library directory to a flash drive or another location on your PC so you can copy it back if you made a mistake.
