Just in case anyone is wondering…
If you don't know, SilverLight is the Microsoft answer to Flash.
If there's some website that has videos or other content that you want to see but they chose to use SilverLight, not all hope is lost.
Just go to the download page for the SilverLight plugin. If you are using Opera, it will tell you that "This browser is not supported blah blah blah…".
Ignore that bullshit and just download it. Then close Opera and install it.
Be sure to remove any pre-existing version first, or it won't work.
After the installation takes place, reopen Opera and go to the plugins page. You should see the SilverLight plugin already enabled. Congratulations, and welcome to the fantastic world of SilverLight content. :-|