Windows 7 brightness slider suddenly gone
Brightness slider in power plan settings recently disappeared.
How to fix it?
Solution 1:
The solution is:
Start -> Control Panel -> Hardware and Sound -> Device Manager.
In the Device Manager window, look for “Monitors”, then right-click your monitor and select “Uninstall”. Be sure to also check the “Remove driver” option. Once removed, click the “Scan for hardware changes” icon.
Voila. “Adjust plan brightness” returns, mystery solved.
References:
Wayne Khan's Blog
Microsoft TechNet