Use this registry file to fix brightness problem for Lenovo z500 Touch:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0000]
"FeatureTestControl"=dword:0000ffff
[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0001]
"FeatureTestControl"=dword:0000ffff
Reboot your Windows, enjoy!
