ATI x800xt Graphics Card freezes when playing 3D Games like flight simulator

Greetings,
Usually that happen once the resolution of your monitor cannot meet the desire need, it depends the kind of monitor that you have even if you change different kind of video card, its still happend.
Try to change the resolution to lower one.
Here's the step
1. right click on the desktop ( a place where there is not icon on your screen)
2. choose properties
3. then settings
4. adjust the screen resolution to lower settings some on the color setting
5. then ok.
Thanks.