@theducks
Funny, when I try using an empty folder as the location of a new library, it works fine. In fact, if I try selecting a non-existent folder calibre will tell me there isn't an existing folder, and fail to create the library.

Although it will show an error message if "The folder ______ is not empty. Please choose an empty folder."
This after people turned their Desktop into their calibre library, and messed
many things up.