Not some much of a question but some info on a Mac program.
Music Folder Files Not Added v1.0
This application will list the file paths of the files in your designated “iTunes Music” folder which are not in iTunes’ library. Additionally, you can select a parent folder and its contents will be compared to the iTunes library. Options to Add a selection of found files to iTunes or move them to the Trash.
http://dougscripts.com/itunes/scripts/ss.php?sp=musicfolderfilesnotadded