Help with ogm videos please.

Hi, i've got some ogm videos and have some problems too:

When the movie starts,the sound starts before the movie, for example, any one talks but the dialog sounds before they move the mouth. I've tried changing the sound dispositive, but it sounds very bad.
My pc is crap but is a:

P2 350 MHZ
448 RAM
Geforce 2 mx 200
Sound blaster 16 <-- crap crap crap

There is any thing i can do to make it work fine? please help