Squealing Noise in the accessory area alternator, water pump?

[emmvette]

I have a squealing noise (fairly loud) coming from what sounds like the passengers side of the front of the engine. The noise is high pitched "whirring" noise. Definitely from something spinning as apposed to a drive train noise.
I noticed it the last time I drove the car and thought I had a vacuum leak, it was fairly quiet. Yesterday I popped the hood to listen to it and when I revved the engine the noise all of a sudden got much louder. I started it later in the day and it started off fairly quiet and then got noisy after 10 seconds of easy driving so pulled it back into the garage for some disassembly. Its loudest behind the alternator. I did a little search on the forum the other day and seemed like a few similar posts resulted in bad alternator. I removed the alternator and took it to a local electric rebuild shop and they tested it and it tests good and then they put it on there run stand and spun it up to 3,000 rpm which is faster than I'm guessing it spins on the car. I took it to them with the fan and pulley still installed and that is how they ran it. It made no unusual noise. He handed it back, no charge, and suggested I look for some other culprit and said it didn't need to be rebuilt, but he would do it if I wanted. I thanked him and took it home. "No need to fix what ain't broken."

At this point, is there a way to diagnose and figure out what is the problem, or do I just need to to randomly replace items? That isn't what I'd like to do.

I realize noise reverberates in the engine bay so its hard to track things down. And now, nothing is hooked up, so I'd almost rather pull the water pump now while I'm right there then to put things back together, start the car and then pull it back apart. I listened with a mechanic's stethoscope yesterday, but it didn't really help. I didn't try to put it down by the water pump due to the belts moving. Seemed like a bad idea.

Any suggestions for this novice mechanic wanna-be??? I do like working on the car, and its the only way I'll learn, but I want to be smart about my approach.