I was looking for this info all over and never really found what I was looking for, so I thought I'd post it here in case anyone was interested. I picked up a 1TB external USB hard drive and it arrived yesterday. I plugged it into my DISH DVR and activated the port (that $40 charge is a scam, yet I still paid it). Once it formatted, DISH showed 930GB available, which is about right. Oddly, everything on the external shows by file size, as opposed to video length on the internal drive of the DVR. I transferred about 8 movies/shows to the drive overnight. Took about 2 hours (USB sucks). But it's all there, just fine. Amounted to just about 12 hours of "HD" content. Interestingly, it only used up 94GB of space. By my figures, I should be able to hold in the neighborhood of 110-120 hours of "HD" content on this external drive. Much better than I expected, given that the 722 DVR I have holds 55 hours on a 750GB hard drive. Maybe it really only has a 500GB drive. Another interesting thing I discovered is the varying file sizes. One 2-hour movie used up over 6GB of space, but another 2-hour movie used about 3.5GB. Both recorded of a Cinemax HD channel. I find that curious. I wish there were better sorting options for content on the external drive, but it is very usable for watching shows directly from it. The backward/forward scanning features are a touch choppy, but otherwise very watchable. So if you're wondering about expansion capacity and how it works with a DISH DVR, here's your answer. And the hard drive I bought (an 1TB Acomdata pureDrive, which has very high customer reviews) cost $118 shipped from Amazon.