I've been thinking of getting a tivo or a dvr type thing, but don't know much about them, and I need some help. 1. a friend of mine has a DVR thing that came with a dish satelite package. can those be bought seperately, without getting a dish? 2. what kind of price range do they run? 3. Will they work with a rooftop antenna, or do I need cable tv to make it work? 4. Aside from tivo or a DVR, is there any thing else that can record multiple shows at the same time? I know these questions are kind of vague, but I don't know much about this stuff.