Help with watching

This is my first post so please try to answe / enyone) Bsplayer works fine and everything warks fine but in some movies i see something like hm how to say. I see picture bute not wery well is something like u look at digital tv and there are some problems like some rendering or distorsion of picture and that comes lately a lot of times. I have pc 1.5 ghz 256 mb ram Graphic card is msi gforce titanium 4200 with 128mb ram so i think that it should be enough. And yes all movies i look from Hard disk not cd.

Thanx