Power Steering Noise

12 degrees out and I started the car but I hear the whining noise, I told my grandson it was power steering fluid. He checked and it was full. After letting the car warm up the noise got quieter but it did whine going to the store and back, although it wasn't loud, it still quietly whined. Could it be the pump or the belt. If I could get under the car i'd check it all my self, but at 72 that's kinda hard for me to do. To bad they don't make cars easy to fix like in the 60's and 70's.