On June 3, 2000, at 0719 hours Pacific daylight time, a Mooney M20F, N9207V, was substantially damaged when it veered off the runway and came to rest in a ditch during takeoff at Cable Airport, Upland, California. The personal flight, operated by the owner under 14 CFR Part 91, was destined for Jean, Nevada. The certificated private pilot and two passengers were not injured. One other passengers received minor injuries. Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that the cabin door came open during takeoff on runway 24 (3,865 feet long x 75 feet wide). He intended to continue the takeoff and return to land and close the door; however, the passenger in the right front seat distracted him. In the time necessary to calm and reassure the passenger, the pilot lost directional control of the aircraft and it drifted off the runway to the left. The aviation surface weather observation at the Ontario, California, airport (6 miles southeast of Cable) was reporting calm wind conditions.