"This copy of Microsoft Office is not Genuine"....?

I bought a computer three years ago with Office2003 already
installed which has worked perfectly, but just the other day
I get a popup message called "Microsoft Office Genuine
Advantage" which will pop up whenever I start Office, and
which invites me to purchase and validate a copy of

Is this some form of virus?

Also, there is a small star permanently affixed to the
bottom left-hand corner of the screen related to this

Please help, Frank