Graphics problem with 13" Macbook Pro

Hi all,
I've been helping my cousin with installing Windows XP on his Macbook Pro... the installation went off fine, however, we seem to be having problems with drivers.
Part of this may be my fault, as I used the Leopard install disc for Bootcamp on Windows, instead of the proper Snow Leopard disc (cousin left his disc at home in the UK). There were some problems with sound and the trackpad in the beginning but we managed to fix those, however, there seems to be some problem with the graphics driver. Resolution is normal, but whenever I try to scroll or move a window, the transition is not smooth at all-- it's like playing a game with an incredibly slow frame rate. Videos muck things up as well...when one is played the screen goes black for a few seconds, the resolution changes, then everything returns to normal and the video plays.
I'm usually pretty decent with computers but I have no idea how to fix this, or even what the exact problem is. I've installed the official Nvidia driver but all that does is add the driver for HD sound. After inspecting system hardware, there was a lack of driver for "VGA controller"-- I'm guessing the computer isn't reading the Nvidia graphics card.
Any help would be extremely appreciated.
Thanks,
arihs