Like everyone else has said, you need to go into Add/Remove and choose Nvidia Display Adaptors (mine was 140meg!) and remove everything, right back to VGA driver. Then reboot and choose the Nvidia 40.41 drivers.
I was sceptical at first about the performance but my two benchmarks (quake2 and rtcw) give me a good idea how a driver performs and 40.41 is a keeper!.
p3 + geforce3 ti200
I tried quake2 @ 1024x768 32bit demo1.dm2
I tried rtcw @ 1024x768 32bit checkpoint
is the benchmark I use for testing out the new display drivers. You will need to rename the extension to dm_59 for wolfmp 1.33. I have a bench.cfg in my wolf\main directory which basically does this to save time typing..