At 1145 eastern time, a Piper PA-46-350P ran off the runway upon landing at Laconia Municipal Airport. The pilot and passenger were not injured. The pilot said he attempted to obtain an airport advisory on the Unicom frequency but got no response. He entered a left downwind for runway 26L and maintained visual contact with a Mooney that was on final approach. He observed no abnormalities during the Mooneys landing. He proceeded with the landing and noted the windsock was limp. As the Mirage touched down, it veered dead left, slid off the runway and struck a snow pile. As the pilot walked to the FBO, he noticed that the runway was approximately 85 percent covered with ice approximately to 1 inch thick. The pilot said his preflight weather briefing stated the runway at Laconia had been sanded due to thin, patchy ice.