NIS 2009, do I install from fresh, or enter product key?

Hi all,

 

Last year I purchased NIS 2008 3 user disc pack from Amazon. Shortly after installing, I was offered the free upgrade to 2009, which I did.

 

However, it is now time to renew the subscription, but it worked out cheaper to buy the NIS 2009  3 user disc again from Amazon instead, so my question is, do I uninstall the present version, & install the new one from fresh, or should I just try registering the new product key?

 

Many thanks,

 

Ian.