wirepaladin

A friend just gave me his old Ariens.  It worked fine for about a week.  The engine starts on the first pull, and the drive wheels turn, but the auger does not move--this was preceeded by a squealing sound.  There is no obstruction that I can see.  I poured hot water on it just to make sure there was no ice jam, but it still would not move.  I took the cover off, and both belts looked ok.  Some people suggest replacing the auger belt.  How is this done?  Or could it be a shear pin?