Why might you wish to mute the Windows sound but not mute the speakers?

First responder: Well I like to mute Windows sounds from the control panel so that while I listen to music streamed from my computer I can use the computer and not have to listen to distraction computer noises.

Second responder: If you would go down to the speaker icon in your system tray, you will see the Word "Mixer" under the slider. Clicking the mixer will bring up a window which gives a slider to each of your open applications. One of these will be the Windows Sounds, which you can mute independently of all other open applications. This is fairly useful for someone who doesn't want to hear Microsoft's OS yelling at them when something horrible happens, but still wants to hear iTunes.