I have had cable for a number of months now and when I subscribed received both the main Nextbox 3.0 unit and another unit for a second TV. I have only just now decided to use the second box but it seems as though it is only wanting to output in 4:3 format and not in 16:9 like the main box. I have HD channels as part of my subscription. I have the second box hooked up to my PC running Windows Media Center if that matters.
Your 2nd box... which exact one is it? That you say NEXTBOX... i am guesing the 2nd one is a Cisco 4642??
That you have it connected to your MEDIA CENTER.. its connected via the coax tv cable OUT of the box, then into your media center? THAT would by why its only 4:3. The coax out, and composite out.. only output in SD, 4:3
For HD to be outputed (and in 16:9), you need to connect via HDMI or component. To do this into a media center.. requires one of the SPECIALTY tuners with the HD inputs.
While some media center tuners, are set up to TUNE HD Digital signals.. they can not decode the ones sent across the rogers lines by itself (why the box is needed in the first place)... BUT it doesnt output that same signal out the coax out, etc. Its a steped down SD version.. mostly for the older TVs, etc that dont have the HD connections.