Very nice tip from music0. It can trick even experienced users many times.
As to adrian936 question in regards to short the pins, here is a definition I found: "A jumper is a removable wire or small plastic or metal plug whose absence or placement on a piece of hardware determines how the hardware is to be configured".
Usually they are found in many places on motherboards and older hard drives. You have to place a jumper on top of a pair of pins on the audio connector (in this particular case one jumper onto 5&6 pins and another onto 9&10. Follow the schematics provided in this thread.