here ya go avie.
the tensioner pulley is spring loaded so you can pull it loose with a wrench to wrap the belt around the last wheel. otherwise it's almost impossible to stretch the belt. you can tell if it's bad if the spring doesn't move back, or move at all. it's actually very common and i wouldn't doubt if alot of the members here have a shot spring and they don't even know it. it's ok to have a shot one on, but if you need to replace the serpentine belt or any pulleys you would need a new tensioner pulley.