to check the belt take it off and look for torn ribbets on the belt when you bend it... usually not always that can cause a missalignment to the pulleys and once you got the belt off you can check the pulleys... i would usually just replace the tens. pulley because those are the likely causes of squeeling BUT i would replace the belt before anything. just check the belt for any tears or if it looks worn out when you bend it. spin all the bearing type pulleys to see if they cause vibration due to fault of the pulley if they spin with a nasty sound usually its a bad pulley.
