Updated to windows 8.1 and now can not adjust my screen brightness on my Lenovo P400. I tried updating the display driver through the device manager and it told me there were no available updates.

Hi,

Have you tried to change sceen brightness at the below of Power Option in Control Panel? if not, please have a try.

if no use, please try to reset Power setting for test.

Generally speaking, this problem probably caused by hardware driver problem, such as Graphic driver, Power manger, motherboard driver. You can try to reinstall them for test.

If problem persists, you cant ry to contact Lenovo support for further assistance. 

I am having the same issue. Did you find a solution to the problem?

• Edited by threegirlsss Tuesday, December 10, 2013 9:22 PM

Hi,

Have you tried the method above for test?

Generally speaking, this problem probably caused by Graphic driver problem, please check and make sure your Graphic driver is compatible with Windows 8.1.

In addition, also make sure your motherboard and chipset driver was upgraded to be latest.

If possible, also please upgrade your BIOS to be latest.one

Be warned.  Flashing BIOS is a risky process.  If power is interrupted during the update your machine will be rendered unusable.

Reboot the computer and when it shows Lenovo use the brightness button and it will brighten.

No.  The problem is that the VGA Display adapter is incompatible with Windows 8.1.  The solution is to go back to the VGA adapter version 9.x, or uninstall 8.1.

This driver worked for me

http://support.lenovo.com/en_US/downloads/detail.page?DocID=DS031547

(I hope that's allowed to be posted here, just a link to the drivers page)