From what I've heard, this is a common problem with realtek sound cards. Unless it was fixed by one of the patches.
Yes, this is a Realtek issue.... and no, it's not fixed. They've recently released some new drivers for their Realtek HD audio, and they're no better than before.
Thank Mara that my wife has "agreed" to let me get a sound card this coming weekend. I really hate motherboard chipset audio with a burning passion.
I went to the skyrim folder as you directed, but all that was there was SkyrimPrefs and saves. Anyway clicked skyrim prefs and found the audio section, changed master to 10 and nothing.
There's something else you can try.
If you have Windows Vista or Windows 7, go to your Sound pannel and turn on Loudness Equalization.
Like I said before, I'm at work and I can't step you through that process. There is a video on YouTube that will show you how to do it. Just Google it and it will show up.