I am in the market of buying a Apple TV, and know that it comes with 40 GB or 160GB HD. I don't have a lot of money and do have extra external hard drives and was wondering can I have the apple TV pull the movies from a external drive? If not am I forced to use my computer to copy them from the external HD to the mac, in itunes and then do it that way? If that is the case why the option of 40 GB and 160 GB? Please clarify for me if you would be so kind.