Videos not playing when embedded in a browser

Hi

I wonder if anyone can help me with a problem I am having running MPEG-4
Videos in IE7 using Windows Vista.

I have several videos embedded in their own web page that start
automatically, when a user visits the page. In Windows XP using Media Player
8 and 9 the videos play with no problem. In Vista however the video either
starts to play and then after three seconds stops or does not play at all.

If I choose to play the videos in Media Player (not embedded in the browser)
they will play all the way through.

There are no error details and the pages with the videos on are on our
intranet.

Has anyone come across this issue or give me an idea on what the problem
might be?

Thank you in advance.

Regards

Richard