the pilot's improper in-flight planning/decision to land on the contaminated runway, the stuck thrust reverser solenoid resulting in partial deployment of the right engine thrust reverser, and the pilot's inability to maintain directional control of the airplane due to the asymmetric thrust combined with a contaminated runway. Factors contributing to the accident were the wet, snow-covered runway, the airport's failure to remove the snow from the runway, and the pilot's failure to recognize the reported hazardous runway conditions by air traffic control.