NIS renewel question

my computer came with norton internet security already installed,i was given 2 months' subscription free and after that i have to renew it.Now i have a few more days of subscription remaining so i buy another NIS for renewal,do i have to install the cd and enter the product key or just enter the product key without installing?

 

 

guys pls help thx for your time.. (:

 

 

[edit: Changed subject to reflect issue.]

Message Edited by shannons on 05-30-2009 10:46 AM