You (and others with similar issues) might want to review THIS THREAD for a discussion of DirectX vs OpenGL.

The short of it is that you need to check and verify that you have the latest drivers for your video card in order to use OpenGL - which is the best and preferred mode to use. DirectX will work, but all those great enhancements and "shiny things" you paid for with the card are sitting on the shelf unused unless you are using OpenGL. (OpenGL uses the card's circuitry and RAM to process imagery, while Direct X uses the PC's processor (bypassing the video card), slowing the system somewhat.