Screen tearing happens when the videobuffer is updated during a screen draw. Screens refresh pixel by pixel from left to right, top to bottom. Tearing occours when the upper portion of the screen shows one fully rendered screen, while the bottom portion displays the next rendered screen. this is most obvious in horizontal movement, and not what I think your problem is. To verify, turn on vsync in the game or force vsync in your graphics driver settings. This will synchronize your FPS to some multiple of your refresh rate so your rendered frames are in sync with the monitors refresh rate, preventing you from seeing the top of one rendered frame, and the bottom of the next rendered frame.