Strange problem with mp4 files

[makada]

I downloaded a file from youtube using keepvid.com. I opted for the high-res file, so I ended with a mp4 file.
The problem now is that when I play this mp4 file (a nursery rhyme song for my son) on my laptop using vlc , I can see the video and listen to the music and the children singing.
However when I play the same file on my desktop using vlc, I can see vidio and can hear only the music BUT cannot hear the children singing!

i am using Win Xp SP3 on both my desktop and laptop.

Is some other codec required to play the mp4 files properly in vlc? Are these codecs inadvertantly present in my laptop as a result of some other program installation which are missing in my desktop?

The vlc version in both systems is 0.9.8
What I cannot figure out is why only the music and not the human voice??? I thought if I had an audio problem it would be an all or none phenomenon. But this partial one has stumped me.

Any ideas?

[Jean-Baptiste Kempf]

So you say that VLC can play it on one machine and not the other one?

[makada]

So you say that VLC can play it on one machine and not the other one?

Yes...exactly.

I compared both my laptop and my desktop to see if any multimedia software present in the laptop is helping vlc play the file properly. But both the computers have near identical software installations ( including itunes, qtime, real)

The only extra software on my laptop is ulead studio.

[Jean-Baptiste Kempf]

You should try to change audio output et audio device

[makada]

You should try to change audio output et audio device

You are brilliant....
The audio output in audio device was set at stereo. I changed it to mono......And it worked. I can hear the music and the children singing.

But why is there music and no voice when stereo is selected?

[VLC_help]

Is that a multichannel audio file? Or have you changed your stereo balance from start -> run -> sndvol32 ?