could be the pump or the box. if the steering shaft turns and the wheels dont then it is one of those. if you have a pressure gauge you can test the pump and see what you have. were there any symptoms before hand? did you change anything recently? the steering boxes are known to fail but usually they fail slowly. did you hit anything that might have snapped something internal in the box? one thing you can try is adjusting the box. there should be a set screw with a jamb nut. losen the jamb nut and turn the set screw clockwise a quarter of a turn and try it. if no results repeat procedure. if still nothing return set screw to origional position. it is either not the issue or is completely shot.