Hello, Refinco, what operating system and web browser are you using?
Silverlight should work fine in most web browsers on Windows xp, Windows Vista, Windows 7, and MacOS.
On Windows 8 or Windows 8.1 you will need to use a desktop browser instead of the modern Internet Explorer with the address bar at the bottom.
If you are using a Windows RT tablet like (the Surface or Surface 2) then Silverlight isn't going to work, but you should be able to view panoramas here on the site alright with the HTML5 viewer and the new Photosynth preview http://photosynth.net/preview (which uses WebGL, not Silverlight) should also work for you.
If you're using Windows Phone, Android, or iOS, you can't install Silverlight.