I think this will get you in the right direction.
Right click on desktop and goto display properties,then settings,then advanced and the under the monitor tab,you'll probably see plug and play for monitor type....Select properties then driver then update driver and follow the directions from there.
I'm assuming you have the current inf drivers on a CD somewhere,if not,go on net and try to find them or see if XP will find them at Microsoft if you choose the auto update instead of "install from a list or specific location" Good luck.