Use VLC. It's open source, and will play anything you can throw at it.
http://www.videolan.org/vlc/
If you still get juddery images, the problem could be your PC - take it to a friend's and see if the problem persists.
http://www.videolan.org/vlc/
If you still get juddery images, the problem could be your PC - take it to a friend's and see if the problem persists.