squeeling noise

suspecting that this is the serpintine belt, but just making sure. when i start my car up and drive it and let it warm up, and then come to a complete stop with the idle at about 900, my lights dim and there is this loud squeeling noise that i can hear from inside the car with the windows up, and the idle also drops to about 700. now when i rev it to about 3k it will go away, but then when i let it idle for a couple seconds again it does the same thing. what is it?

alternator pulleys might be wearing down and causing friction, which stops the alternator from charging.. thats just a shot in the dark

altenanor is junk need new one there about $100-$130

actually, alternators are free, hahahahah, you've got to remember i have a whole other 240 sitting at my house....