One month old Mac user! I bought a Western Digital MyPassport Esstential 320 gb and would like to have it so that I can back up my MacBook Pro every month or so. Is there a way to have it back up only when I want to and not have it auto back up? I just want to be able to plug the hard drive in whenever I want to perform back ups. Also, I've heard that even though the MyPassport says Mac compatible I will still have to format it, could anyone explain to me what I'll have to do for that? Thanks a lot for the help!