Annoying sound problem

Hey everyone, I'm using Windows 7 x64 Ultimate and i have rather annoying sound problem.
As I'm listening to the music in Winamp while playing some game, say Warcraft 3 (or doing anything that makes sound for that matter), everytime there's a fight (like 10 units bashing on eachother), Winamp sound turns down, like if sounds from the game get in conflict with other sounds, turning eachother down. As soon as the said fight ends, music goes back to full volume. Also this happens with every player (WMP, GOM etc...) and every source of sound, even while watching Youtube clips.

I've got Realtek HD on-board sound (abit a9n32x), using latest drivers (2.40).
I even tried using older drivers but with no luck.

Try this...

Right click on the Microsoft speaker icon in the task bar.

Select, Playback devices.

Go to the communications TAB, select "Do Nothing", see if the problem still exists.

You can also select the "Playback" tab, select "speakers" and take a look at the options under "Properties"
Specifically, look at the advanced tab.

Ap

Nothing I tried to do there works -.-

Tried disabling those 2 options under advanced-exclusive mode, checked disable all sound effects under enhancements... no luck.