Is a 1TB external drive large enough to use as a TimeMachine backup for a 1TB iMac? I ask because I may have screwed up. I have already placd an ordr for a 1TB external drive, thinking that is what I am going to use for my TimeMachine backups. Last night I was reading my "Switching to the Mac" book and it said to use Timemachine, your back up drive needs to be adt least as large as the disk you are backing up. Obviously, these are same size, but have I shot myself in the foot? I hate sending things back, so worst case, I now have a 2TB iMac I guess. If this external is really to small for its intended use, what size drive should I be looking for? Sorry if this is a really basic question, but I'm a Mac noob. Thanks.