goto
http://www.nvidia.com/content/drivers/drivers.asp and go through the START HERE COLUMN and continue through step 3 (dont click the link that says linux and BSD drivers that will take you to the page without the documentation) when you get to the page after completing the START HERE columns find the readme. txt file
it contains all the info you need to picking the correct driver , to instlalling that driver to edit you XFree86config file afterwards......
I strongly suggest you read this....
hope this helps
Peace