help, I cannot play video full screen from some sites as I used to be able on XP system

Hi, I can play the CNBC video (for example,
http://www.cnbc.com/id/15840232?video=275787763&play=1) in Firefox
with full screen options. I had Windows XP the default player is
windows media player version 11.0.6000.6324

Now I have a Vista and Firefox cannot play the same video in full
screen (no option to choose for full screen), the default player is
also media player, version 11.0.5721.5154.

Please help. Is this to do with video card?