The Zune is a Microsoft MP3 player. Although you usually use it with a computer to upload music to the portable device, it is possible to connect the Zune to the computer and play music through the speaker system. This is helpful if you don't have access to your own music library and you want to listen to your music with friends.
Plug one of the 3.5mm ends of the cable into the headphone port on the Microsoft Zune.
Connect the opposite end of the cable into the "Line-In" or "Mic" port on the computer. This is usually where you connect a computer microphone.
Click the volume icon to the right of the clock, then click the "Mixer" link under the volume controls. Adjust the "Mic" or "Line In" volume in the window that opens.
Turn up the volume on both the computer speakers and the Zune, then choose an audio track and push "Play." The audio now plays through the computer speaker system.