Check if the indicators on the remote volume control are lighting up when sound is played.
Make sure the volume from the source (PC/DVD) is not muted.
To check/adjust volume for the DVD …
To check/adjust volume for PC, left click on the speaker icon (shown in image)in the System tray on the right bottom corner of the screen. In the pop-up dialog , the Mute checkbox should not be checked. Move the slider on the dialog up/down to increase/decrease the volume.