Sorting out video playback (various problems)

[El Moose Monstero]

My computer is a mess, basically - but I'm into my project and don't really have the time to sit around reformatting and reinstalling everything under the sun to clean it out. So I've currently got a video I'm trying to watch, it's xvid format, I've got all the right codecs according to one of those codec identification tools - but when I try playing it in VLC, BSplayer or DivX, I get choppy playback which results in soundlag. When I play it in media player, I don't get these problems, but WMP doesn't remember where I am in the file, so if I have to interrupt it, I have to start watching it from the beginning all over again and I can't advance it to the point I was stopped in.

If anyone has any pointers on how to correct one or both of the problems, I'd appreciate it. I know the file is good as I've watched it on friends computers, so I know it's not that.