Norton AntiVirus 2009 Won't Install on Vista HP Notebook

I can't install Norton AntiVirus 2009 on my HP Notebook running Vista.  I am installing from a 3-User CD that I bought from a retailer.  I get to the screen where it asks for the CD key and the license agreement.  I fill in the key, but the "Agree & Install" button doesn't work.  I am stumped.  Please help.

 

Thanks,

 

James Collins