Download the 326.29 Beta driver, it offers support for Windows 8, Windows Vista, Windows XP and Windows 8.1 both 32 and 64-bit. This is a developer driver and seems to add opengl 4.4 support.
Driver 326.29 for Win 8.1, 8, 7, Vista. It is a developer driver for desktop and laptop. No modified inf needed. No need to disable driver signature enforcement. This driver is WDDM 1.3 on Windows 8.1 Preview. It is a complete driver package, containing 3D drivers, HD audio driver, PhysX.