What can be wrong with my Internet Explorer 8.0 installation/settings?

I can not run any WebPlayer on any page. I see plugin download icon instead of unity content, on running it get “installation failed” message. I use IE8 on Windows xp. Everything works fine in other browsers.

Well is your current date and time set correctly? I had the same problem when trying to download unity and figured out my date and time was not correct so it would not give google a secure https.
P.S Google chrome is were its at