Windows 7 uses WDDM 1.1
An advantage with WDDM 1.1 allows you to have multiple video cards from different companies; installed at the same time. (In this case, Intel IGP and Nvidia discrete video).
While a WDDM 1.1 driver is backward compatible with WDDM 1.0 OS (Windows Vista), Nvidia's Optimus Technology only works with WDDM 1.1 infrastructure at this time.
From here: http://windowsteamblog.com/blogs/win...-graphics.aspx
Optimus only works today on Windows 7. NVIDIA’s software and Windows 7’s driver model (Windows Driver Model – or WDM) and APIs (like DirectX and DirectCompute) allow for the kind of experience Optimus provides.
Vista (and older) users? => LOL! Tough titties! You'll need to upgrade to Windows 7. (Don't be surprised this situation continues in the future with WDDM 2.0/2.1 and future versions of Windows.)
Right now, Linux's graphics stack can be considered "under major renovation". Until it has finally stabilized and matured, Nvidia won't bother with things like Optimus Technology under Linux; and will continue to do things their way (as seen with the closed driver)...Linux users will need to suffer a few more years as the underlying infrastructure evolves and matures...Patience is a virtue.