I have a box running as a mythtv box (well actually its not running just now since am reinstalling it for various reasons, but that is another story :-).

Its connected to a TV which adverts it self as running 1280x720 pixels, but the outer rim is covered by plastic so I would like X to only use the centre part of the screen for drawing.

Mythtv have an option to do this which works perfectly, but as soon as I want to run a "regular" app I need to guess where the menus are since they are hidden by plastic.

Back in the days when you configured X by hand on CRT monitors I remember there being a small app that did this by adjusting the Horizontal sync etc. but I have not been able to locate that (and I'm not sure it would work with today's screens).

Its a Nvidia GeForce 6150 card connected by HDMI to the TV