Still, you have to install the new drivers, which still support your card right?
Since you have to do that, the driver should support resolutions available on Widescreen monitors, unless the cards so old, they have discontinued it in the driver revisions.
Found something thats free that should help:
"PowerStrip provides advanced, multi-monitor, programmable hardware support to a wide range of graphics cards - from the venerable Matrox Millennium I to the latest ATI and NVIDIA Crossfire/SLI solutions."
So it should allow you to define resolutions