Norton is just fine, all you have to do is to update and to use your brain .. though 2005 is a little heavy if you don't have lots of RAMs ...
20 days later
256 on a laptop are enough for N2005?
well yes, I think so .. though I recommend you to install a liter Anti Virus. BitDefender maybe ?
i am using NAV2005 and i have 320 mb of ram....works perfectly
7 months later
I'd recommend you to use AVG, anyway, just running a single AV will not always get the wormstrojansviruses on your machine, head over to http://housecall.trendmicro.com and do an online, free, full system scan and be sure and have the 'Auto Clean' checked. Also make sure youve visited Windows Update and applied all security patches. Regarding spywares etc. HijackThis is an excellent tool to discover and disable hijackers, but it requires expert skill, for more information regarding HJT point your browser to http://www.aumha.org/a/hjttutor.htm and rtfm. Also make sure to update those programs before using. You can log your results generated by HJT and post'em anywhere on this forum and I'll be happy to guide you step by step.
Norton SYmantec is fine IMO, but it doesnt catch spyware. You need another program for that.
I use Symantec antivirus corporate edition + microsoft antispyware
I used to have lavasoft ad-aware as antispyware before.

Why symantec antivirus corporate edition? Light memory requirements, no virus definition subsription (update when you want), neat and discrete, centrally managed (very useful for more than 10 PCs, you can update all av clients from the server, lock options so that users dont change them, get alerted when a client detects a virus, etc...).
I got rid of NAV 2005 and downloaded Kaspersky I don't regret it one bit, it uses less system memory and has detected viruses that NAV didn't detect.
I am downloading Kaspersky right now. I'll tell you what I think about it when I start using it.
what do u think of ZoneLab ?
Excellent Firewall (if you know how to configure it)...worse than Kaspersky as antivirus