No Internal audio Option available.....

I don't have any Built-In Audio from my PowerBook 17 speakers... In the System Preferences - Audio, the only Output option is Digital Audio. In the Audio Midi setup the Default output is Built-In Audio and the Output settings are 44kHz 2ch-16bit but the only source available is Digitgal Out......?

Analogue Line output works fine, and I can see red optical activity from the line/optical output, but when disconected I get no audio from the built in speakers.