Check if the indicator on the remote volume control is lighting up in both channels when sound is played.
Make sure the audio balance from the source (PC/DVD) is centred .
To check/adjust balance for the DVD …
To check/adjust balance for PC, right click on the speaker icon (image here) in the System tray on the right bottom corner of the screen and click on Open Volume Controls. The volume control dialog should be displayed. All the balance sliders in the dialog should be centred between the 2 speaker icons.