Kaire,
Try double checking your audio settings in the Realtek HD Audio Manager in the Control Panel (Classic View). Make sure it is set properly for the type of speaker setup you have. Take a look through this to see what to check. Play with different settings to see if one will do the trick for you.
http://www.vistax64.com/sound-audio/85436-new-realtek-hd-audio-driver-released-3.html#post502777
Shawn