I just installed Enemy Territory on Windows 8.1 and ran into a problem – I could not adjust the brightness (gamma) in the game. The slider would work and the brightness would flicker but then return to the default value.
I tried adjusting the Compatibility mode for the game and tried adjusting the gamma using the console in game:
/set r_gamma 1.5 /r_ignorehwgamma 1
The error in the console was this:
set DeviceGammaRamp failed
The solution turned out to be very simple – just turn off f.lux and everything was OK again!
If you have not heard of f.lux before it is a program that makes the color of your computer’s display adapt to the time of day.