[Animal]

Think NWN is using Direct X. I'm running 1024 by 768 with 64mb textures and antialiasing at 2x and the game runs slicker than pig snot.
Zidane, your machine should be able to handle the game, but not a high resolutions and detail settings. Start by using the lowest possible settings with maybe the 16MB texture pack and try working up from there until it starts to slow down.
The problem is most likely the GF2MX can't handle all the textures your trying to push at it. Make sure that you have AGP Fast Writes Enabled in your computer BIOS.
I'm not real familiar with the Celery, but if memory serves it's running on a 100MHZ FSB, so make sure your memory is running at the speed as well.
XP is quite the resource hog, so you may find that the extra ram will help, but like I said it's most likely the video card.
One final thought, download the latest chipset drivers for your motherboard as well as they handle your AGP (video card) bus. Good Luck everyone. It's an awesome game.