Alejito Burrito,
The native resolution for that panel, considering that it's designed to be a monitor primarily, is 1680 x 1050. The black lines you're seeing are a result of showing a 720 or 1080 picture on a 1680x1050 panel. I'm not sure, but I don't think the XBox has that resolution available, however most video cards for computers would work with that resolution.
On that panel, it's not possible to show every pixel while maintaining the resolution. I'm not sure why it would be cutting off the sides. Would it be hooked up to a cable box sending a specific resolution or picture format?
--HDTech
I have a very confusing issue with the "Just Scan" setting when using the Xbox 360, connected with an HDMI cable.
I only recently read about "Just Scan" turning off overscanning and doing 1-to-1 pixel mapping. HOWEVER, while I do get extra picture on all four sides using "Just Scan", the picture ALSO fills up the entire display (no black bars).
This doesn't really make sense, because the set is 16:10 while the Xbox 360 (set to 1080p) should be outputting at 16:9. I love the option to turn off overscanning, but "Just Scan" is stretching the image vertically and I can't wrap my mind around why this would happen in supposed 1-to-1 mode.
I'm currently testing it on a 1080i HD signal (Conan on NBC, to be specific) and it's the same thing:
- "Wide" shows no black bars
- "16:9" shows bars on top and bottom, more picture on left and right
- "Just Scan" shows NO black bars, EVEN MORE picture on left/right/top/bottom
Does "Just Scan" maybe just mean "show every single pixel in the signal, but also fill the screen"? I assumed it was an option to show every pixel while maintaining native resolution.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic