When updating to Windows 8.1 new hd4000 drivers were automatically installed. After this installation the internal display of my notebook is not working anymore. There is no picture shown on it (but the backlight does light up).
This happens not only within windows, but starts right from booting. VGA and HDMI output are working fine. When I look at the intel control panel it only sees 1 display which is the external one, the internal is not detected by the software.
I have tried to revert back to older drivers and even installed windows 7 on a second partition, all with no luck.
My system is an Asus N56VZ, i have atached my dxdiag to this post.
If you are able to use second screen, this means the problem is not related to drivers, this is a hardware issue with your internal screen. Drivers are working because you are getting display through another monitor.
Contact Asus for possible warranty options.