Are the smears horizontal only? If so, try reseating the cable between the monitor and the computer. Another alternative, if your monitor and computer both support DVI or HDMI or some other digital display cable, is to switch to a digital signal. With an analog cable, your computer has to translate the digital information into analog, and then the monitor has to re-translate that analog back into digital before displaying. With a digital cable, you avoid all those conversions.