Installing Internet Security 2011 on a 2nd computer (laptop)

I purchased Norton Internet Security in May 2010 for $54.99 and it said it could be used on up to 3 PCs.  I only have 1 PC, however I now have a laptop and would like to install it on my laptop.  However my invoice says I have protection for 1 PC and "Remaining Activations" has "None"... I don't understand.  Who do I contact to find out how to get this installed on my second computer?   I purchased it online and have automatic renewals since 2006.  I hope someone can help me with this.

Thank you!

Kellene