The aircraft collided with mountainous terrain about 30 miles northwest of Cortez, CO. The pilot was on an IFR flight plan and had been advised before flight of hazardous icing conditions enroute. When the aircraft iced up, the pilot reversed course and, even though descending below MEA, he managed to stay clear of the terrain until he turned southeast toward Cortez over higher terrain. He was out of direct radio contact with Denver Center because of his altitude. Denver was able to relay through an airliner until all contact was lost at 0927 MST. A search was initiated and by ELT help the aircraft was located 3 hours after radar contact was lost. The pilot's handbook for the Beech 35 stated: 'WARNING, FLIGHT IN KNOWN ICING CONDITIONS PROHIBITED.' Examination of the wreckage revealed that the aircraft impacted tall pine trees in a wings level 10-15 degree nose low attitude. The aircraft came to final rest in a densely forested snow-covered area between 2 large pine trees. Shoulder harnesses were not installed in the aircraft.