problems readind video files

Just installed geforce4 mx440 agp8 64mb
i have : windows98se, 512mb memory, athlon 2000xp, directx 9; display
iiyama crt 411
When i try to read a video it is completely blurred like a mosaïc;
impossible to see
the normal display is correct.

Formerly i had an old ati with 4mb memory and the only problem was the
display of videos was a bit jerky and it is the reason why i changed...

Any idea ?
Thank you for the help
Jean-Marie