Hi, I have been using a 250gb external hard drive to backup my MacBook Pro through time machine and it is nearly full. My wife has now got a MacBook Air that needs backing up. Can i delete some of the old backups of the Pro to make space for the Air backups or would that be a bad idea? Or would time machine do it for me if I try and backup the Air to it? Also can i make a partition on the External hard drive for the Air backups without losing the backups of the Pro? Thanks.