Norton Anti-Virus 2006

I noticed that amazon.com has a $20 rebate for NAV 2006. I already have Norton Systemworks 2003 installed (& I've been purchasing the subscription key ea. yr to update my av protection) so all I really need is a subscription key. But I thought I'd take advantage of the savings fr. the rebate & buy the whole nav program. Since I only need to upgrade, do I do anything differently when I install the nav 2006? Or is it a straight install?