If the belt and pulleys aren't all gooped up with belt dressing, sometimes regular old Crest toothpaste will polish everything up enough to make the noise go away. Just smear an amount about the same as what you normally use on your toothbrush on each side of the belt, and start it up. It will sound like hell to begin with, but should quieten down within a few minutes. May sound crazy, but it's worked for me and a bunch of other folks many times. If they are
all gooped up, they need to be thoroughly cleaned, either with a strong alkaline cleaner or brakleen, whichever seems to do a better job.