On August 16, 2002, at approximately 1340 mountain daylight time, a Piper PA-25-235, N9791P, was destroyed during a forced landing following a loss of engine power near Boulder, Colorado. The commercial pilot, the sole occupant of the airplane, received minor injuries. Mile High Gliding Inc. was operating the airplane under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the glider-towing local flight which originated from Boulder Municipal Airport approximately 30 minutes before the accident. The pilot had not filed a flight plan. The pilot said that he checked his flight time and fuel gauges (including fuel low level indicator light) before takeoff. He said that while towing a glider, he experienced fuel exhaustion. The pilot said he performed a forced landing to an open field, but the wind changed from a estimated 15 to 20 knots to no wind situation when he got close to the ground. He said that the airplane stalled from about 8 or 10 feet, hit the ground, and nosed over. The engine was crushed back, and the left wing was separated from the fuselage. The density altitude was calculated to be 11,361 feet.