Compaq EVO screen has "blank" columns

My screen has columns which are not viewable. There is about an inch of viewable clear space, followed by a garbled column about an inch wide, then another inch of good viewable space, then another inch of a garbled column, and so on all the way across the screen from left to right. It looks like a grid of vertical blind columns. I can drap a window left and right and the contents of the window are viewable as I move it left and right. I hope I'm making sense here. I'm not sure if this is a hardware issue or if i have a display setting wrong.