The driver depends on the particular hardware, and can usually be found on your manufacturer's site if you search under Support for your model. Go to asus.com, go the the Support area, and search for your particular motherboard model. Do you know the model?
Alternatively, a very clever member here posted directions on how to identify any hardware that needs a driver. See the second post here: http://www.tomshardware.com/forum/274306-45-video-controller-compatible-driver-windows-free-download
, from Saga Lout.
Please satisfy my curiosity: how do you know that this is a driver