I don't know, I thought gamma had more to do with graphics and Software than the PC itself. Most photo apps and even games have their own gamma adjustments so try that. If there is a gamma adjustment for the card itself, it would be in its configuration area (in XP right click a blank spot on the desktop and select properties,then open Settings and Advancced then click on your Graphics card tab) if not each software may have its own in its configuration area.