I'm trying to upgrade to Snow Leopard on both my iMac and Macbook and I just purchased an external hard drive to back my stuff up before I install. However, what I'd like is to use this external hard drive for both machines. So when I have my external hard drive plugged into my iMac, would it be possible to have Time Machine just back up only that disc image and when the external is plugged into the Macbook, then Time Machine can back up the MB disc image? Admittedly, my knowledge of this type of thing is little, so thought I'd ask. If it is possible, how would it be done? I currently have Carbon Copy Cloner installed. Would it be done there? Thanks!