ollie that site is nothing more than a link for
Driver Detective. The NVS 400 series that it is referring to is the current versions of that card (NVS 440 based on the same NV43 chip as in the old 6600 card; and the NVS 420/450 based on G98 which from what I can find is a derivative of the 8400GS).
The NVS 400 is nothing more than a NVS 200 with two cores on it, and based on the even older NV17 chip which is the old MX440. Any search for a
driver for this old card is pretty much fruitless as it is a DirectX 7 based card, and there will never be a Windows 7
driver for it.
About the best you can hope for is to try the XP driver installed in compatibility mode.