HELP – S3 Virge 325 ONBOARD VIDEO CARD

I am trying to find some way to brighten up my monitor display. The picture is fine on certain things, but on some games and pictures for instance, it is so dark I can barely see. I have a HP Pavilion 7270, with onboard S3 Virge 325 card. In the colors it says I get 24-bit, but if you click on down menu for colors, only half the squares have colors. I need to find out what driver or how to set the driver up to get more colors. (I tried monitor on another PC that has ATI card, and I was able to adjust it’s Gamma control to correct picture). I don’t know what to do, help!??? Thank you.