I have had no sound input and output. The System Prefs, Sound, show "No Input and Output Devices". When I plug in USB headset I get normal sound input and output and the USB device is listed in Syst. Prefs under Sound. Another issue with my PB Ti 500 is that the restart remains incomplete unless power adapter is used. However, the battery shows full charge. The restart doesn't proceed beyond the grey just after the Apple icon. The PB works OK without battery, but no built-in sound. Despite these two problems, built-in sound and battery interference with restart, the Power Book G4 works normally. Milan