Brightness tile missing from mobility center, unable to lower brightness

Hi,

To work on the issue, refer these methods.

Method 1:

To permanently change the brightness of the display, follow these steps:

1. Click Start click Control Panel, and then click Power Options.
2. Click Adjust Display Brightness.
3. Change the display brightness of the computer, and then click Save changes.

Note: If the computer does not display the Adjust Display Brightness option, check with the computer manufacturer for updated BIOS to support this option.

BIOS Disclaimer:

Modifying BIOS/ complementary metal oxide semiconductor (CMOS) settings incorrectly can cause serious problems that may prevent your computer from booting properly. Microsoft cannot guarantee that any problems resulting from the configuring of BIOS/CMOS settings can be solved.

Modifications of the settings are at your own risk.

Check by changing the brightness settings, if the settings are available on your computer.

Method 2:

Update the latest graphics card drivers from the manufacturer’s website, and then check if this fixes the issue.

Refer the links to update the drivers.

http://windows.microsoft.com/en-us/windows-vista/Update-a-driver-for-hardware-that-isnt-working-properly

http://windows.microsoft.com/en-US/windows-vista/Update-drivers-recommended-links

Note: If you don’t find the drivers in Windows updates, download the drivers from the manufacturer’s website.

Method 3:

Try to uninstall and reinstall the graphic driver completely from device manager and check if it helps

1. Type devmgmt.msc in start search box and hit Enter.
2. In device manager, expand graphic driver.
3. Right click on it, click on Uninstall.
4. Reboot the computer.

After restarting by default the driver will install successfully.

Also refer:

Using Windows Mobility Center

http://windows.microsoft.com/en-us/windows-vista/Using-Windows-Mobility-Center

Check if it helps.