I have installed Ubuntu 11,04 on an ASUS AT5IONT-I DELUXE motherboard containing an Atom D525 (with its own integrated Intel GPU) and a Next-generation NVIDIA ION GPU. I want to play HD videos and so want to use the NVidia driver with vdpau hardware acceleration. However, VLC is unable to play HD videos even with the its "Use GPU acceleration" option selected.

When I look which hardware drivers are installed (System -> Administration -> Hardware Drivers (if I remember well, I do not have the computer with me right now)), the system tells me that I have one proprietary driver "Nvidia accelerated graphics (version current)". However, this driver is "activated" but not "in use" (last line of the window with the green "LED"). What does it mean? How do I force Ubuntu to use this driver?