I have an ipod that i have used and kept updated on windows for the past two years. I got all my music moved to my macbook and placed on an external hd to keep from taking up too much room on my macbook. The problem i am running into is that when my ipod is connected, in the screen where you can click to update, it says updates only for mac formatted ipods. How do I go about formatting it for mac, and making sure i don't wipe out all my itunes music?