Problem with a new video card

I have bought a second hand computer for my partner, pretty basic.

Dell Optiplex GX150
20GB hard drive
512mb ram
pentium 3 processor
ati radeon 7000 video card

I disabled the onboard video card, slotted the new video card into a pci slot.
Installed the drivers off the disc.

I only bought this pc to play one game, medal of honor allied assault.
When i attempt to play i get the error in the console "Couldn't Load ui/menu.urc"
I've googled this error and cannot find any solutions. I also tried uninstalling the game and reinstalling, but now the installation window just disappears off my screen.

Any help appreciated