1: The Ti4200 is AGP 4x only. The Ti4800 that was released as a refresh was the 8x version.
2: Im not sure about Quadro cards... it might be a driver bug thats detecting it that way.
3: The card (actually the drivers) supports directx 9. The 4200 will only do directx 8 pixel shaders and effects, but it will run with directx 9 just fine as long as you use up to date drivers. Also, MOHAA isnt directX9, so that deffinitely isnt the problem.
Im a bit confused as to the whole Quadro\4200 thing, so you may want to try different drivers to get that straightened out first. Take out his card and varify that it is a 4200 or a Quadro, then try to get the drivers to install the correct ones. After that, we can work on the game issues.
EDIT: Before you do anything, uninstall the Nvidia drivers through add\remove programs, then use Driver Cleaner
(preferebly in safe mode) to clean out nvidia drivers and then restart and reinstall the drivers.