It sounds like you are in Software mode. Go change that to direct 3d or Open GL. What kind of graphics card do you have? Oh, and check if you have the latest graphics drivers.
how to change to direct 3D - click "configuration", click "video modes", then click on Direct 3D or Open GL.
how to check your video card - right click on your desktop, and click "properties". Then click on the Settings tab and it should say "plug and play monitor on [your video card].