There is a fix on the Bethesda forums for Realtek users for those with low volume/quiet dialogue issues. I tried this myself a few minutes ago and can confirm that the dialogue now sounds clear and loud as it should.
Here is the link to the fix: http://forums.bethsoft.com/index.php?/topic/1260478-fix-for-low-volume-on-realtek-hd-onboard/
Basically go to your RealTek audio manger and set the speaker configuration to 5.1 and uncheck all the optional speakers, but leave the full range speaker settings checked.
That doesn't work, I'm on a laptop :[ any idea on how to fix this? --- http://i20.photobucket.com/albums/b242/Lazer77/9.jpg http://i20.photobucket.com/albums/b242/Lazer77/WOJ.png http://www.xboxlc.com/cards/s2red/Lazer77.jpg