Since sound is fine the problem is probably with the graphics card and its
drivers.
Answers to the following questions will help to isolate the cause.
What make/model of graphics card do you have?
What resolution are you using over what interface to what type of display?
What graphics card driver release are you using?
Have you read the release notes for the driver release you are using?
"Andreas" <ayiangoullis@hotmail.com> wrote in message
news:9F31DE59-C0E7-4AB9-99C2-8C57492992D3@microsoft.com...
> When I open any video file with Vista media player they run fine as long
> as they are in a small window. If I maximize the window in full screen or
> even if I rey to make tyhe window significantly larger, the video starts
> freezing and showing a frame-by-frame view and only the sound goes on
> normally. This never happened on XP.