Having taken delivery of a new helicopter the previous day, the pilot was carrying relatives on short flights over their property. On the second flight, descending through 200 feet for landing, the rotor low rpm warning horn sounded. The pilot applied full throttle and lowered the collective pitch control but this did not restore rotor rpm. As the horn continued to sound he turned the aircraft into wind and attempted a landing in a clear area. The aircraft struck the ground with the heels of both skids and the tail rotor. The tail boom was severed by the main rotor, and the helicopter came to rest on its right side. The passenger suffered bruising as a result of contact with the emergency locator beacon which was mounted between the backrests of the two seats. No fault was found with the engine or airframe which might have contributed to the accident. However, atmospheric conditions existing at the time were such that moderate to serious carburettor icing was probable.