To change the volume levels:
- Click the Volume icon in the Notification Area (looks like a speaker with sound waves coming out of it).
- Click the Mixer link at the bottom of the little window that pops-up.
- You can scroll through the different applications that are running on your computer. Then you can set different sound for each by adjusting the slider controls for each one individually or you can press the mute button to quiet that application.
Note: The master volume control which is labeled Device (the first slider) controls the total amount sound that can be outputted from the whole computer. Even if you have all the application sliders maxed out, they can't output more sound then is allowed by the master control slider.