The Inq reports the NVIDIA G80 GPUs require special drivers as DirectX 10 hardware is a bit different than DirectX 9 or earlier.
If you go to nvidia.com download page you will learn that the Geforce 8800 series needs a special driver. In fact, Nvidia has three different variations pf driver: one for Windows XP or Media Center edition, the second one is for Windows Server 2003 X64 Edition and the last one supports Windows XP Professional 64 bit edition.
It seems that Nvidia silently moved from a Unified driver architecture to a completely disunified one.
A driver for Windows Vista is still not available.