Depends on what your TV supports. I also have a 36" 4:3 tv that doesn't support 720p. So if I want to watch Cinema 10 or anything else not 1080i, I have to leave it on 1080i. The problem with this is that 4:3 SD will have a border all around, effectivaly turning your 36" into a 25" TV. If you turn the output on the STB to display native resolutions, all 4:3 SD content will take up your whole screen.