what does this mean?

Hi - I'm new to this group. I'm not very computer "smart" so I need help with this. When I booted up my computer today, I had a notice that I need to register my Microsoft windows software (or something like that) and I have 3 days left in which to do it. We have had this computer for 4 years and have had Windows XP as our OS all that time. There is a little blue star shaped icon on my system tray that takes me to a Genuine Mocrosoft Software site where they want me to do a Windows Genuine Advantage Plug-in installation. What is this all about? I don't know if it's important or not, but I use Mozilla Firefox.

 

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