Calibration structure, method, and code for correcting non-orthogonal misalignment of a computer-generated image that is projected onto a large screen touch-detecting display, so that a computer-generated image appears substantially where the display is touched. Structure / method / code generates at least four calibration marks, respectively, substantially proximate four corners of a projected image to be displayed on the display. Structure / method / code, responsive to a touch on the large screen touch-detecting display where each of the four calibration marks is displayed, identifies horizontal and vertical coordinates of each touched location. Structure / method / code calibrates the projected image to the display after the four calibration marks have been touched. Structure / method / code, responsive to another touch on the display after calibration, displays a computer image substantially at the location of the another touch.