Hi,
It’s a great opportunity to assist you with the issue. As you reported that the issue is with the function keys. We need some more information to assist you in a better way.
1. Did you make any changes after installing windows 8 and updating drivers?
2. Did you try to install the display drivers in compatibility mode?
Here is what you need to do to run the display drivers in compatibility mode.
a. Download the display drivers from the manufacturer’s website.
b. Right-click on the driver setup file and click on Properties.
c. Click on the Compatibility tab and check the box Run this program in compatibility mode for and select Windows 7 operating system from the drop down.
d. Click on Apply and click OK and run the file to install it.
Hope this helps and please get back to us if you have any more question.