Don't forget the idler tensioner pulley as well! My A/C Compressor died and after it was fixed, the squealing never stopped. We replaced the idler tensioner pulley (and the tensioner for good measure, it definitely needed it) and the squealing went away; Basically the bearings were shot and it made the belt slip. If you want to test the idler pulley (It's on your belt routing diagram on the passenger side strut cover) take off the belt and spin it; if it grabs at all, it's gone, that thing should spin free and smooth.
