No Sound From Built In Speakers Options

[Atahualpa]

From one day to the next I do not hear any sound coming from the built in speakers on my PowerBook G4 1GHz. When I check the audio preferences, it displays Headset copnnected to the audio output as the chosen output and I cannot really choose anything else. I believe before it said always Built in Speakers there, unless I'd plug the Mac via firewire to an external audio module. Could it be that I lost or accidentally deleted some sort of driver or other piece of software necessary or is this some kind of hardware damage? (I haven't really using my computer as a freesbie lately!)

Thanx in advance, Atahualpa