Do the few that play slow have very high resolution, and do they use a modern codec like Windows Media Video 9, divx 5, or xvid? If they are chances are that your processor is underpowered and can’t keep up. You can try shutting down all programs to allocate as much processor power to movie playback, but there’s only so much you can do.
My general guideline is any processor under 300 MHz playing high resolution divx 5 movies will drop frames or play the sound and video out of sync.
I’ve downloaded some bit torrent movies lately and some of them play really slow. and some of them the sound and pictures don’t match. like the sound is at normal speed but the picture pauses and freezes and then show a couple pictures.
Is there a way to adjust the frames per second?
I have a really slow computer but the other movies i downloaded play fine. just the few that are slow.