On October 1, 1997, at 0830 central daylight time, a Cessna T210N, N5168A, operated by a commercial pilot collided with the terrain when the landing gear collapsed on touchdown. The landing was being made on runway 17 at the Hector International Airport, Fargo, North Dakota. The 14 CFR Part 91 flight was operating in visual meteorological conditions without a flight plan. The pilot was not injured. The airplane was substantially damaged. The flight originated from a private airstrip in Hillsboro, North Dakota, at 0800. The pilot reported he extended the landing gear 3 to 4 miles prior to touchdown at an airspeed of 120 knots. He reported that he kept his hand on the gear lever until it was down at which time he made a visual check to assure it was down. He reported that during the landing flare he heard the gear warning horn; however, it was too late to initiate a go-around. The landing gear collapsed as the airplane touched down. Post accident testing of the landing gear system revealed the hydraulic pump circuit breaker would pop when the landing gear was extended leaving the gear in a trailing unlocked position.