You may receive a distorted image when the cable is loose or defective. Disconnect the video cable going from the back of the computer and verify that no pins are bent, burnt or broken. Once verified re-connect the monitor cable. If the refresh rate is not properly set the monitor may have a wavy or an appearance that lines are going down or across the monitor slowly or fast, this may also cause a flickering affect. A distorted image can be caused by magnetic or other types of interference. Verify no speakers, fans or other magnetic devices are close to the monitor.