My new imac will be arriving in the next day or so and I need to purchase an external hard drive to back everything up. I am so confused after reading so many different threads... I want to be able to put all photos and videos on one external and then back up both my machine and my photos/videos... So - am I correct in thinking to get maybe a 500GB external drive for my photos/videos and then a 1tb for the back up of both the machine and the external drive? My machine has a 320 GB hard drive. Help? Does this sound right? I have never backed anything up in my life but want to start out using my mac correctly. I was also looking at iomega drives....any thoughts? I want something small and tidy - hence my purchase of my imac.