window media player 11 for vista

helloo...
hope someone could help me here i am running window media player 11 with
window vista ...when i log in a site to play an audio it doesnt play in the
media player 11...while when i try to do the same in my other computer which
has the window xp and window media player 11 it does play ...
any reason to why and how can i play the media player on my vista computer..
thank you for yr help
allure