There should be one belt and a TENSIONER and also an IDLER.
Both the tensioner and the idler have the same bearing in them that is in some roller skates! These bearings wear out after a while and make noise before coming apart.
It is always best to replace BOTH at the same time.
This is a common question about squeaking. Almost all the time it is one or both of the above.. Though sometimes it is other... such as bolts coming loose on the mounting of the alternator or A/C compressor and causing a squeal..
If these bearings havn't been replaced in a few years then it is time anyway. This is a cheap repair anyone can do with a small amount of tools.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />