Quake3 is very dark in Windows2000

The Quake3 1.2x or above point releases should resolve this problem so make sure that you have the latest point release. This is from the Geforce FAQ but it's the same for all video cards with the brightness problem under Windows2000. A couple of cvars that aren't mentioned in the GeforceFAQ that can help are r_intensity and of course r_gamma.

Type the following command at the console:

/r_ignorehwgamma 1
/vid_restart
and see if it helps.

You can also try the following:

/r_ignorehwgamma 0
/r_overbrightbits 0
/vid_restart
This should mean that the brightness slider works as usual.

If that doesn't help, try typing the following commands at the console:

/r_mapoverbrightbits x
/vid_restart
where x is a value from 2 to 3.