Sorry for asking a noob question, but I already have five computers licensed to my itunes (mac pro, Macbook Pro, MBA, and two PCs). Does ATV count against this five license limit? I would like to buy a couple of ATVs to connect them to TVs but didn't know if I could authorize them. Also, I've bought a ton of TV shows and movies from itunes so my library is currently about 800 gigs. Will any external HD connect to ATV or is something I should be looking for?