I'm using WinXP on a Gigabyte GA-8N-SLI Pro motherboard. It has onboard AC'97 Realtek sound.
If I use their surround test to check my 5.1 setup all the speakers work as expected. Also works fine if I play surround sound from a video in VLC or Potplayer.
A stereo source plays from the centre, front left, front right and bass speakers as expected.
The problem is any sound from a browser - I've tried both Firefox and Explorer - only comes out of the front left and right speakers. Any other stereo source would normally play from front left, front right, centre and bass.
I have tried the latest driver from Gigabyte's website ver A3.92 and the latest Realtek driver version A4.06.
To recap: surround works fine with everything but web browser sound only appearing front left and right (no bass or centre).
(oh and I also am using this computer with Windows 8.1 update on another drive - different drivers obviously - and the sound is fine with everything including the browser)
Any ideas what's wrong here and what I can do to fix it?