Open iTunes, Select FILE, Select ADD FILE or ADD FOLDER to LIBRARY, when the box opens search for your Napster Library, locate your music, select all songs/folders you want to add and click OPEN.
I started out with Napster and was able to add my music to the iTunes library. I haven't deleted Napster so HOPEFULLY some of the gurus (b noir, toonz) might have some suggestions on not deleting your music but just the program.
Let us know if this works for you.