VIDEO CARD

I am running XP SP1 Home Upgrade. I bought an ATI 64MB DDR Video card (9000). I downloaded ATI’s most current drivers. In high end game play the video card will freeze up anywhere from hours of play or even five minutes of play. It works fine during desk top or low end games. Now the monitor seems to lose a signal and the PC continues to work, but I still must do a reboot to regain visual use of this machine. Anyone know where the incompatablilities are? Appreciate some help.