I put Windows 8 on my HP Envy 15 the day Microsoft released it, and for the most part I’ve been happy. However the control over the brightness of the screen stopped working. I would tap the keys for the brightness control, and the indicator would appear as if it were adjusting the screen, but the screen brightness didn’t actually change.
Well “Adrynalyne” has found the solution, and fully details every step over on his post, “Fix Brightness Control for Windows 8 AMD SG Drivers.”
You can read everything there, but if you’re just looking for a super quick answer, find this registry key:
Double click “FeatureTestControl” and change the value from “f842” to “f940”.
My laptop is using HP provided display drivers. If yours is not, you may want to refer to Adrynalyne’s article for more options.