Why can't Win8.1 adjust the screen brightness?

First, I tried to use a solution that was found on the Internet and generally solved the problem that Win8.1 screen brightness could not be adjusted:
One way to use more online is to solve Win8 by modifying the registry. 1 The problem that the brightness of the screen cannot be adjusted.
The specific method is:
1, use the Win + R combination shortcut to open the run dialog, and then use the :regedit command to open the registry.
2, open the Registry Editor, expand the location:
HKEY_LOCAL_MACHINESYSTEMControlSet001ControlClass{4d36e968-e325-11ce-bfc1-08002be10318}
Then change the value of KMD_EnableBrightnessInterface2 in 0000 and 0001 to 0.
3. After the completion, restart the computer.
Note: If there is no 0001, only change 0000, and if you can't find the KMD_EnableBrightnessInterface2 registry key in these two items, you can create a new one, and the new type is REG_DWORD.
Some netizens successfully solved the problem that the brightness of Win8.1 screen could not be adjusted through the above methods, but the author still did not solve the problem through the above methods.
Second, try to update the computer driver
After the author used the driver wizard, Lu master and other software to detect whether the computer has a driver problem, through the detection found that the CPU and motherboard driver available updates, but ultimately in accordance with the problem of upgrading and updating, still not solved.
Three, tried Windows update
Enter Win8.1 Windows update, detected several updates, but after updating the driver, the problem remains.
Fourth, try to uninstall the discrete graphics driver
Because the brightness of Win8.1 screen can not be adjusted is usually related to the system settings or graphics card and other devices, so try to uninstall the driver of the discrete graphics card, because the notebook is i7 alone, In the graphics card device, you can find the CPU comes with a graphics card and a discrete graphics card. Therefore, the author first uninstalled the discrete graphics driver and restarted the computer. Eventually, the screen brightness could not be adjusted.
At this point, the author has been a bit skeptical about whether there is a problem with the notebook screen, but in the end I still want to try again.
The next operation is to use the driver wizard to install the discrete graphics driver again, and then this time I uninstalled the HD4000 core graphics card that comes with the Core i7 processor. Surprise is that when the HD4000 core graphics card is uninstalled, The screen of the notebook turned out to be magically bright, and the screen brightness can be adjusted normally.
With this computer failure, you can understand that the brightness of the notebook screen of the author is mainly caused by the core graphics driver problem that comes with the CPU. Although the software such as the driver wizard has not detected the problem, but finally After uninstalling, you can restore the screen brightness, and finally install the driver without problems. If you encounter Win8.1 screen brightness can not be adjusted, then you may wish to try the author's ideas and solutions.