the way that i do this.. is i transfered all of my music to my external...im actually doing that as we type.. then i changed my music folder to the one on my hardrive...but if you want to still save the majority of your music to your computers internal... then wut i would do in that case is make the external harddrives music folder your music folder in itunes prefs and then whenever you are downloading music that you wnat on your interenal... eject the external and unpluig it then download the music... it will automatically download to your users music folder... thats what i would do