The helicopter pilot and three passengers were circling over rural terrain at an altitude of 150 feet above ground level and approximately 219 pounds overweight for the flight conditions when the pilot slowed to 10 knots with a tailwind. The helicopter began to lose main rotor rpm and the low-rotor aural warning sounded. The pilot lowered the collective in an attempt to maintain rotor rpm, but there was insufficient altitude to recover. The helicopter hit the ground with the tail rotor first and the body of the helicopter landed hard and skidded forward, crushing the left skid. The main rotors flexed downward during impact and severed the tailboom. The pilot reported that there were no preimpact mechanical deficiencies, and that the accident would likely not have happened if he had turned into a headwind.