I had a user that needed to switch between a headset for Skyping and the audio on the Smart Board. While there is not a simple one-click solution that I know, changing the settings is not TOO bad:
In Control Panel, Audio/Sound:
On the "Audio" tab, there should be a drop-down under "Default Device." The default is usually "USB Audio Device," which is the Smart Board.
Click the drop-down and choose the built-in audio instead (in this case, "Realtek HD Audio Output").
Click "APPLY" then "OK" and close out any Control Panel windows.
Sounds will now play through the "green" plug in the back of the computer. To swicth back, return to Control Panel and change the "Audio" device back to the USB Audio.
Hope this helps!