On September 10, 1998, at 1908 central daylight time, N7965W, a Piper PA-28-180, collided with a tree and the terrain during a forced landing in International Falls, Minnesota. The private pilot and passenger were seriously injured. The airplane sustained substantial damage. Visual meteorological conditions prevailed for the 14 CFR Part 91 personal flight. The airplane was operating on an IFR flight plan. The flight originated from Menominee, Michigan, at 1500 cdt. The pilot reported that prior to departing on the cross country flight, he had the airplane topped off with fuel. He reported he then taxied away from the fuel pumps, went through the "normal IFR checklist", got the local weather, then taxied to runway 21 for departure. He reported that after takeoff he maintained an altitude of 6,000 feet and he had an approximate 20 knot headwind. The pilot reported that once level at 6,000 feet he leaned out the mixture and maintained 2,400 to 2,500 rpm. The pilot reported they departed Menominee using the left fuel tank. They switched tanks every 30 minutes during the flight. The pilot reported the flight was uneventful until reaching Ironwood at which time he deviated 3 to 4 miles off course to avoid weather. He reported that upon reaching Lake Superior the headwinds lessened and they picked up ground speed. The pilot reported that between 1800 and 1830 they were burning fuel from the left tank. He said they intentionally stayed on the left tank for an additional 15 minutes, "...so that I could conserve all the fuel possible in the right tank so that if there was any kind of problem I would know that I had all my reserved in the right tank." He reported he switched to the right tank at 1845. During a telephone interview the pilot reported the right tank gauge indicated slightly less then 1/4 tank at this time. He reported that, "...within a minute or two..." fuel "starvation" occurred and the gauge indicated "0" gallons. The pilot continued to state that "Shortly after switching to the right tank, I am not certain exactly how long, suddenly the engine coughed and stopped." He reported he turned the fuel pump on then switched to the left tank and the engine started again. The pilot advised air traffic control of the situation and was informed that the airport was 10 to 12 miles away. The pilot reported, "We very quickly burned out the fuel that remained in the left tank and the engine stopped again." The pilot selected a field in which to land; however, the airplane contacted a large pine tree prior to reaching the field. The right wing separated from the airplane and the airplane impacted the terrain. Post accident inspection of the airplane failed to detect any usable fuel on board the airplane. The airplane was inspected by a mechanic from Einarson Flying Service, International Falls, Minnesota, who reported there was no evidence of any failure/malfunction of the fuel system which would have resulted in a loss of fuel. The airplane departed with 48 gallons of usable fuel onboard. According to the aircraft owner's manual the fuel consumption is 10 gallons per hour at 75% power. The airplane had been airborne approximately 4 hours and 8 minutes when fuel exhaustion occurred. The pilot reported they were on the ground for approximately 10 minutes prior to takeoff. The aircraft owner's manual did not provide fuel consumption information regard the full power climb to 6,000 feet.