You will have to have a different key in order to update Norton.
Instead of paying for the update, you could try free antivirus and firewall programs.
A list of recommended programs can be found here: Freeware Replacements For Common Commercial Appshttp://www.bleepingcomputer.com/forums/topic3616.html
There is no one size fits all when it comes to computer security. What works well on one computer may not play nice on another system. On the system with 2006, when did it start to slow load? Was it fast loading in the past? It's possible that for some reason Norton has decided not to play nice with the computer.
The programs in the link above are all excellent ones you can try. If you choose one and you don't like it, it can easily be uninstalled so you can try another one. No money lost or wasted.
Edited by Queen-Evie, 25 July 2008 - 10:49 PM.