Volume error on L4D

Hi people. I dont know why but, when I play Left 4 Dead or Garrys Mod the process volume on Volume Mixer goes on minimum but a "ghost" volume icon stays on maximum.

I always have to minimize my game and get my volume on maximum again, each round start (when survivors were overwhelmed or survivors win).

When i have an SS i post here.

And only to say, im so happy that, I've downloaded the video driver from ATi website, but I dont needed to install it, I play all my games (L4D, CSS, Gmod, TF2...) with the WDM driver with all filters and everything with the same FPS i get with the ATi driver installed.

you say you d/l your video drivers, did you check device manager to make sure your sound (onboard/card) is working correctly?
I love l4d btw, pm me your steam name so we can play sometime.
Goodluck!

TimeShift said:

Yes i've discovered in another forum:

Control Panel -> Hardware and Sound -> Adjust system sounds -> Communications tab -> Select Do Nothing.

Hehe I was just about to say thats why your volume was ghosted