I have an HP Pavilion DV6 laptop which has a horizontal line on the display. I checked with an external monitor and the video was shown correctly, so I assume there is no problem with the GPU. The laptop's screen is new and I have changed the cable as well, but I am still having the same problem. Could someone please offer any advice?
Changed the cable where? It's most likely an issue with the thin ribbon cable connecting the screen to the rest of the laptop in the hinge -- sometimes it snags and gets damaged. The horizontal line artifact you described occurs most often in this situation.