Silverlight not in Explorer 8 add-ons

I am unable to use Skyplayer because it claims that Silverlight 4 is not present. However it is and is showing in the programs list. I am using Internet Explorer 8 and when I Look at the list of Add-ons, Silverlight is not listed, so this is obviously the root of the problem. The question now is how do I get Silverlight included?

Thanks John. I have uninstalled Siverlight, rebooted the system and then reinstalled Silverlight but it is still not listed.