Hey, my Lenovo y50-70 has both Intel HD Graphics 4600 and Nvidia GTX 860M and i can't use 4K resolution on it after i reinstalled the PC from Windows 8 to Windows 8.1 Pro. I have looked through many forums, i have googled the <Mod Edit> out of it and i just cant find any solution in which makes me able to use the 4K screen on my laptop. (Max res: 1920x1080). I have changed the settings in the Nvidia Contolpanel and put the power settings to High Performance.