Note that there is no circuits inside the 702 to support an internal hard disc.
A piece of SD trivia: When the boxes were first released, they did offer a version called 722RAW which had no HDD. It was for people who specifically wanted to install their own. I put an 80G in mine. I think they took only 10 orders before they quit offering that option. When I call for support, no one even remembers what that was.