It sounds like they deployed on a Windows XP Embedded platform. This is NOT WINDOWS XP. So while the embedded version is XP, at the same time it is not so this can truly upset those that had such a system when they think something can be done.
My only thought of what may work is a VGA splitter box. That way the monitor ID comes from the old monitor and you get a bigger display on the big TV.
Other than that you are back to the maker of this system to tell them to issue a version for your new setup.
I have a digital imaging software(x-ray) that operates on a windowsxp computer. The only job of Windows is to run this software. If you shut down the software, the entire computer will shutdown. I can however get into control panel while the imaging software is running, by using the windows key. Here is my dilemma... I want to swap the original smaller monitor out for a large TV monitor to display the digital images. The original monitor that came with the computer will fit the imaging program entirely on the screen when I set the resolution to the highest for that monitor, 1024x768. If the resolution is lower, there will be parts of the imaging software screen I cannot see on the computer monitor (I can see about 80% of the actual interface). When I have the interface perfect on the old monitor and switch the VGA to the larger TV monitor, while the computer and both monitors are on, the interface screen comes up on the TV perfectly. But I cannot switch the VGA over like this every time. When the VGA stays in the TV and I turn the computer on, the windows screen starts up and the ratio is perfect. When the digital imaging program starts to run, I can only see about 70% of the interface. Changing the resolution in control panel does not work with the TV monitor, like it did with the original computer monitor. I have tried to switch over to the alternate screen as well, allowing me to try other resolutions, but none of them compress the entire interface on to the screen. I have tried every way I can think of to fix this problem, to no avail. Any help would be appreciated.