|I would guess it is either or. You can look at the sound settings to see if both can be used. Sometimes there is a setting to use a device exclusively. If one is found, untick it. |
Speakers work best when they are used as a system. Combining TV speakers with your PC speakers will probably result in a less satisfactory sound than using the PC speakers alone. This all depends on factors you haven't provided.
If you have HD sound, open the HD sound manager and change the speaker settings there.