Your AC compressor is siezed. If there is a separate belt, just remove it until you have a chance to get the compressor replaced. If not, you will have to get the clutch freed up so that it can allow the engine to rotate, at least, if not get the compressor replaced.
Most if the cars with a single serpentine belt have a speed sensor in the compressor that shuts it off if it slows down too much. This works unless the clutch is also locked up, which sometimes happens.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!