How to Fix  Brightness control "unavailable"  

issue on Windows 8.1 Pro / windows 8 

Simple Remedy Is Here

Jest install  "Adjust Laptop Brightness " 

After installed.....  Working fine in Windows 8.1 Pro 

Its a paid version, if u don't like to buy  simply Uninstall. Don't worry, your Lap brightness key's will work fine and you can Adjust brightness on laptop 

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Adjust Laptop Brightness

Save your laptop battery and reduce your eyestrain.

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Adjust brightness on laptop Adjust brightness on Mac running Windows. The software allows Windows users to adjust brightness. If brightness cannot be adjusted, the software changes screen contrast instead. This is a big difference from other software on the market. PC users running Windows iMac, Mac Air, Mac Mini, Mac mini users running WindowsA tuning utility to change screen brightness for HP, Compaq, Dell, Gateway, IBM, Lenovo, Sony, Toshiba, Fujitsu, Panasonic, Samsung, Acer, MSI, and Apple laptops. It helps you to save your battery and your eyes as well as the back light of your screen or monitor. This releases adds support for Apple iMac and All-in-One desktop computers of other brands. Support Windows 8, Windows 7, Windows Vista, Windows XP, and Windows Server operating systems.