The pilot was landing after completing a practice instrument landing system approach in bright day conditions. The pilot reported that he extended the landing gear and flaps when he was about three miles from the airport. The airplane crossed the threshold of the runway and was just about to touch down when the pilot noticed that the landing gear green indicator lights appeared not to be illuminated. The pilot applied full throttle and immediately raised the landing gear and flaps. During the go-around attempt the airplane settled and the propeller struck the runway. The pilot held full power and a nose-high attitude as the airspeed decreased. The airplane struck obstructions on the side of the runway, resulting in substantial damage to the left wing. It then came to rest upright approximately halfway down the length of the runway. An inspection of the aircraft systems by a Federal Aviation Administration inspector revealed that the cockpit lighting dimmer switch, which controlled the illumination intensity of the landing gear lights, was set to the “Night Dim” position.