The settings folder...you have to open Calibre --> Preferences --> Micellaneous, then click on the "open Calibre configuration directory" button. After you open it, close Calibre, then you can copy that entire directory to your backup. I copied that, then all my libraries, to a 300gb hardrive, which I plugged into my Netbook, but I had to install Calibre Portable and run that, then point it to all the libraries. So I effectively have a working backup. Although I don't know that I'll sync it to my desktop ever again, or not.
