I have a 2000 Explorer XLT. The power steering has just started to make a noise when I turn the wheel.

Check the belt. Look up how to do a belt tension check. Check the fluid level. If that all is ok, consider replacing the pump.

At one time or another I have changed maybe a half dozen powersteering pumps on Explorers from 96 to 2003. The last one I changed was on a v6 99 model year. There is a good possibility (v6) that the pulley will have to be removed with a puller and reused. Therefore you will need a pulley remover. Ford is notoriously known for power steering squeel when they go bad. Take it or leave it, do not purchase a rebuilt unit, purchase one new. My last experience with AutoZone was I got three rebuilt units that squeeled worse than the one originally going bad on the vehicle. Although I can remove the pulled rather quickly with the proper equipment, it is stil a pain to have to do it three times in one afternoon. Another suggestion, and you will need assistance, is after installing the new pump, continually add fluid with the return hose in a proper container. Pump new fluid through the entire system, including the rack, uncle it's clear, not the black color you will notice. Recirculating the old black fluid through your pump only runs the risk of clogging up the small filter inside the pump.

power steering pump will not turn I put a new one and this one did the same thing