MSI RS482M4-CSIP Manual page 93

When you are playing the first audio source (for example: use Windows
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 front 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.
Using Audio Function
A-9