Anytime TouchSmart is running, it runs all of those applications in the background to allow for the UI that is there. Unfortunately, there's no way to mute different applications individually within TouchSmart.

You could mute the system with the keyboard, the volume panel on the right side of the TouchSmart PC, or at the top right of the TouchSmart application window.

Alternatively, if you just want to mute browser or music, go to the Windows Desktop. On the lower right hand corner, next to the clock, there should be a little speaker icon. Right-click that and choose 'Open Volume Mixer'. From there you can mute individual applications, such as TouchSmart Music and Browser.

--Andrew