Playing Movie, but no sound

I am a new user of Directory Opus.
When I am clicking on a .VOB file the movie is playing in the Viewer Pane.
But I can not hear the sound of the movie.

.VOB's are usually DVDs. DVDs are usually AC3 audio encoded. I'd install AC3Filter so it can decode the audio.

(This was written at the same time as ktbcrash's reply, above, so there is some duplication/overlap.)

You may need to install (or just re-register) an audio codec for whichever audio format is being used by the .VOB file (usually MPEG-2, AC3 or DTS).

FFDShow is a good bet, as it can decode just about anything and is fairly self-contained.

Note that 64-bit Opus requires 64-bit codecs, so be sure to get the 64-bit version of FFDShow if you decide to try that. (On the other hand, most other video software is 32-bit and uses 32-bit codecs, which can account for some differences between Opus and other tools when playing videos.)

Links to FFDShow and other information can be found here: HOW TO: Enable/fix playback of various media formats in Opus.