Under the control panel, click display, settings, advanced, then color. "Color" is a general ATI driver tab, though the Rage Fury drivers may list this feature under another name, been to long since I've used this chipset. Do not confuse this option with "Color Management." CM is the Windows interface for loading monitor color profiles as supplied by your monitor manufacturer, though many monitors are not packaged with color profiles since the built in controls often surfice for most users.
You should now be able to adjust the brightness settings for both desktop (2D/3D) and overlay (video) rendering function. Set the function, apply, leave the color applet running, play your game, then reset as desired. Not the best solution, but I also sometimes have to perform this same task when playing older games with my notebook's Rage Mobility graphics chipset.
Robert Richmond