This happened way back in 2k4. I was a supervisor for help desk support for HP pavilion desktops. One of our customers called in saying that HP had committed a fraud by selling him a new system with a DVD drive which threw out the DVDs and that he was gonna sue us! He had the latest model that we had released just a few weeks back.
Now this seemed to be a serious case and the supervisor was needed which was me. I calmed the guy down and asked him to describe what exactly was happening. He elaborated that after placing the disc on the tray when he presses the button, the tray goes in but the disc falls out. Now this was weird. He had tried different discs but still the problem persisted. As I pulled out the product page, I asked him which one of the drives was giving him the problem, the one at the top of the system or the one below that. To this he retorted none of the drives are at the top. Now I was confused. I asked him where the drives were. He promptly said, at the bottom of the tower. Then it hit me, the guy had kept the tower inverted! Needless to say he wasn't happy with his own stupidity once I provided him the solution.