Norton antivirus 2911

On September 17, 2010 I purchased a 3 computer version of the above product.  I installed on my desktop and 2 laptop computers, BUT ONLY ONE asked for the product key number - the 3rd computer.

 

Now I am getting reminders everytime I turn on the other two computers to say my antivirus is running out in 18 days.

 

Why is this happening?  How can I put in the product code number onto my  desktop and laptop?

Thank you,

Mrs. Betty Allen