Thanks guys, I feared the encryption may be the biggest problem to fight.
I am getting an external that I can dedicate for this purpose, so I'll at least be able to keep some favorite HD recordings.
I believe the encryption is on the files stored on the dvr's internal hard drive as well, because I can supposedly play files directly from the external hard drive and can also record programs directly to the external hard drive.
As to why the HD recordings are 6 times as large, I don't know, but they are. I believe the internal hard drive of the 722 reciever is about 320 g, and it has space for about 55 hrs of HD and over 300 hrs of SD recordings. Maybe all are mpeg-4 format.
For clarification, are you saying I won't be able to make data dvds of the files either, because of the linux system? If I can at least store the files on dvd discs, I won't have to own 25 external hard drives to keep a library of HD recordings.
I realize I would have to move the files from the dvd discs back to the ext. hd to play the recording thru the Dish dvr. But that would be OK, for recordings that would very rarely be played.
FYI, more info on the new Dish USB capabilities can be found here
Thanks again for the info.