Click the sound icon in the notification area. It may be muted or been reduced to zero.
Un-check the mute check box if needed and adjust the sound level to your taste.
Double click that icon. It open the main sound controll dialog.
Make sure that the master controll on the left is NOT muted and set to a reasonable level.
Make sure that the WAVE sound controll is not muted and set to a reasonable level.
Electro, April 2012