Sony VGC-RA910G - Manual (Page 235)

Why can't I hear dialogue during DVD movie playback, using my 5.1 channel speaker system?
 Verify that your speaker system is connected correctly.
 Change the computer's audio settings to 6-channel, to match your 5.1 speaker system.
 Change the audio settings in the RealTek ® Sound Effect Manager software program.
 Change the audio settings in the InterVideo ® WinDVD ® software program.
 Change the audio settings in the Media Center software program's DVD settings.
See the section, Connecting 5.1 (6-Channel) Speaker Systems for details on configuring the audio settings in these
software programs.
Page 235