On January 21, 2000, about 1235 Eastern Standard Time, a Mooney M20M, N223KT, was substantially damaged during a forced landing shortly after takeoff from Edward F. Knapp State Airport (MPV), Montpelier, Vermont. The certificated commercial pilot was not injured. Visual meteorological conditions prevailed and an instrument flight rules flight plan had been filed for the flight destined for the Essex County Airport, Caldwell, New Jersey. The personal flight was conducted under 14 CFR Part 91. According to the pilot, a few minutes after takeoff, he realized the engine was not developing full manifold pressure; shortly thereafter, the engine lost all oil pressure. When the engine began to vibrate, the pilot shut down the engine and performed a forced landing to a field. Examination of the airplane by a Federal Aviation Administration Inspector revealed the engine's cowling was covered with oil, and the engine's crankshaft seal had been "blown outward." Ice was observed in the engine crankcase breather line. Additionally, a "bend" was found in the breather line near a clamp that was installed over the breather line vent hole. There were no other discrepancies found with airplane. The weather reported at MPV, at 1232 was: Winds from 320 degrees at 12 knots; Visibility 8 miles; Few clouds at 2,100 feet, Broken clouds at 2,600 and 4,200 feet; Temperature 0 degrees F; Dewpoint minus 9 degrees F; Altimeter 29.52 in/hg. According to the pilot, the airplane was last flown for 2.4 hours, on January 14, 2000. The airplane was kept in an unheated hanger; however, the engine was preheated using a built-in engine heater to an oil temperature of 40 degrees F, just prior to engine start.