Your question is a little hard to discern based on the wording and me not knowing your mechanical aptitude so I will try to cover all the bases. 1st as Dr. drivability said would be the power steering belt which can squeal when turning from side to side but not usually just one side, also happens at startup and when revving the engine. It usually gets quieter as the belt warms up. Tension is the first thing to check but if that is ok it could be because the belt is glazed or worn and sunk to far down in the pulley causing lack of grip. The easiest way to check for belt noises that aren't obvious is to to take a can of spray silicone and spray the belt while the engine is running being careful to not get it on the other belts to isolate the problem. the second squealing you could be hearing is from the tires which could be caused by tire pressure like you said or front end alignment issues. if its usually just one side it's caused from the camber being out from either hitting a large hole or curb or worn ball joints or control arm bushings. When the tires squeal both ways that's a toe out condition it is usually caused by loose tie rod ends. The third way your steering could make a squealing noise is from the power steering pump itself. to hear this just turn the steering wheel al the way to one side or the other while in park, if this is what you are hearing the most common cause is a slow leak causing low fluid level. make sure if you fill it you notice that there are hot and cold fill lines on the stick. this is to allow for expansion of the fluid when hot. you can use plain old dexron atf to fill. if full but definitely the pump it could be on it's way out. Make sure you check the belt first as it can make noise under all three of the tests or circumstances above. Please check back and let us and future readers of this post know what you find.