Norton Antivirus 2008 Installing new product key

Hi,

I have been using NAV 2008 and my subscription is about to expire.

I purchased a new version ov NAV 2008 at Staples for free after rebates.

I try to install it onto my machine and it says I still have 2 days left on the subscription.

How do I use the new product key and get the new copy to work?

Thanks,

Tj