Sony PCG-XG18 Primary User Manual page 70

Click the Start button, point to Settings, and then click Control Panel.
Double-click YAMAHA DS-XG Audio Config.
Select Digital Output and click "ON [All Sources]/Analog out is
muted."
Click OK.
Connect a CD player, an active speaker, or an amplifier to the LINE IN
or LINE OUT connector of the Mini Docking Station to play a CD disc
and experience higher-quality audio.