There is no specific APU driver. To expound on what Wolfshadw has mentioned, the drivers will be the same as what you would be using with the corresponding discreet devices, so there will be the standard HAL for the CPU which should be installed during the initial Windows installation, plus a graphics driver for the graphics portion of the device, plus any ancillary support systems that Windows doesn't already have generic driver support for, should be installed by the chipset driver package.