I have the new iPhone 4 and would like to use my 8GB iPhone 3G just as an iPod. (Removing all apps and previous music on there; I am giving this to my boyfriend to use. So I would like to give him a "blank slate" so he can put as much music on there as he can.) Is this possible without screwing up my new iPhone and the syncing on my Macbook? Or do we have to do this with a different computer, separate from the one I use for my iPhone 4?