Whenever I start my car, an obnoxious squeak comes from my power steering under my hood .. when I slow down or stop, it squeaks; if the weather cold or rainy, it squeak; sometimes when I accelerate, it squeaks. It sounds kind of like metal rubbing against metal, or maybe I'm not used to such a loud noise coming from a car -___- anyway, I want to know what I need to replace to fix this noise; the belt? the pump? or something else?

 

Sounds to me like a loose belt. If it is a high pitch "squeak"
Power steering will "whine and moan" more than "squeak"
I would visually inspect your power steering/alternator belt. Look for signs of cracking.
Try to wiggle it with your hand, it should have a little bit of play. Too loose or too tight can make some noises.

 

sounds like the belt is spinning on the pulleys. check for slack on the belt and adjust as necessary.