I am picking up my new Air on Thursday as I'm giving my son my old MBP. I have a question on how you guys manage space that iTunes takes up. I have about 15 gig of music and over 100 movies. Can you run (for a lack of a better term) from an external drive? I'm not that worried about space other than iTunes. I use the cloud for all my docs and pics. Sorry to be asking such a rookie question but I've not had to think about this before now. Thanks for your time!