On January 23, 2000, at 0900 eastern standard time, a Piper PA- 22, N3814P, collided with a snow bank and nosed over at the Plymouth Airport, Plymouth, Indiana. The private pilot was back taxiing the airplane on Runway 28 (4,400' x 60') in preparation for takeoff when the accident occurred. The pilot was not injured and the airplane was substantially damaged. The 14 CFR Part 91 personal flight was operating in visual meteorological conditions without a flight plan. The pilot reported the runway was covered with approximately 2 inches of snow near the center and deeper snow on the left (north) side. He reported that as he was taxiing, the left main gear contacted the deeper snow and the airplane veered to the left. The airplane then nosed over when it encountered a two to three foot deep snow bank on the left side of the runway. The pilot reported the local winds were from the south/southwest at 12 to 15 knots at the time of the accident. The Plymouth Municipal airport manager reported the runway had not been plowed. He stated the airport was NOTAMed closed and the accident pilot knew about the NOTAM.