Core audio disappeared...why?

Suddenly there's no audio output, the Sound/Output Preference pane is blank.

When starting up Peak 6, it informed me that Core Audio was no longer available. I've been recording tapes output from the earphone jack of a boom box, digitized via an iMic plugged into the Mac's USB slot. This has been my practice for years. Does this mean this antique PowerBook's sound card has failed?

Thanks for any insight,

Greg

PowerBookG4; 1.5 gHz; OS 10.5.8