MSI 945GCM5 Series User Manual page 70

Realtek ALC883/888 Audio
W hen you are playing the first audio source (for example: use W indows Media
Player to play DVD/VCD), the output will be played from the rear panel, which is the
default setting.
Then you must to select the Realtek HD Audio 2nd output from the scroll list
first, and use a different program to play the second audio source (for example: use
Winamp to play MP3 files). You will find that the second audio source (MP3 music) will
come out from the Line-Out audio jack of Front Panel.
A-9