Just got a TiVo HD (stock drive for now). The "default recording quality" screen has a note on it that says something along the lines of recording from digital sources are not affected by that setting. My only input into the TiVo is a digital cable line. When I try to record anything from any channel (High-Def, Standard-Def, premium cable, NBC... any channel at all), I don't even have the recording quality option visible. So, I guess the capacity values (45, 74, 96 and 180 hours) only apply to the analog recordings. I don't have any of those. The capacity for HD content is supposed to be 20 hours. What's the capacity for SD content that is digital? From what I can tell, the answer depends on the compression used by the cable company. I'm using Time Warner Cable of NYC. But a ballpark figure is fine.