If you have all the latest drivers and everything you might be okay. I just got Morrowind and it wouldn't work until I had everything up to spec. I have the same type of graphics card (the II MX) but I've got a athalon 700. The games requirements are similars so, like me you'll prolly have little or no sound and a crappy framerate. You'll just have to see. Think of it as an adventure. A really slow, jerky, gritty quality graphics adventure.
I don't if NWN is going to be as graphics heavy as morrowind tho' so you might be okay. Basically, I just don't know.
DeSoya