First off Welcome to the site, fill in your profile it will help us to help you, goto user cp, click on edit system specs. If you don't know what you have then download everest home edtion it will tell you what your...
Go to Nvidia's web cite and go to the downloads sections and go through the simmple steps of finding out what driver you should use.
Edit: This should work- http://www.nvidia.com/object/winxp_2k_81.95.html
and i don't think it will ever provide a very big performance boost.
I think that in the future when games get more hungry, i will use it. Remeber what top of the line today is only ok tommarow, well sort of,...