Picture quality problem

[iron2000]

Player: WMP9


When played from disc the picture seem to be "folded" resulting in thin vertical lines appearing on screen (coloured not black and white).
WMP9 uses it's own codecs for disc playback(I suppose).


But when playing the ripped vob the picture quality is very much better (no lines).
WMP9 uses Elecard codecs on mpeg2 files.



Is the codec the cause of the poor picture quality?
If so how can I better this condition?



Thanks