What I found is that if it works it does a good job, but the install can be very finicky - if you don't have problems immediately there's a good chance you will somewhere down the line. I also found the problems are not easy to solve, even with Symantec's help.
Also, NAV can slow your PC down, as Sandy110 mentions. You may not notice this much if you have a reasonably fast PC with WinXP/2000.
I use the free AVG now & WinXP's firewall, but generally you'll be advised to use the free ZoneAlarm firewall & AVG or Avast antivirus. G
I used Norton for 3 or 4 years with no problems but when a virus got in Symantic refused to help saying that the version of Norton I was using was too old and they no longer supported it. I was paying them an annual subsciption at the time but they said all that entitled me to was the virus updates. So I deleted Norton and that was a hassle too, installed AVG, it found and deleted the virus straight away. Guess what I use now.
I used Norton for years, but like others I found it expensive, intrusive, resource hungry and sometimes not particularly good at detecting viruses. I have been using Avast (click here) with ZoneAlarm (click here), both free, for about two years and I'm very impressed with their performance and ability to work together.
I have been using Norton software for years. I am currently using Systemworks 2003 and Internet Security 2003. Both perform efficiently and unobtrusively with no noticeable system slowdown. Slowdown can be minimised by sensible setting of program options and background tasks.
I was always a great Norton fan. Recently however I went on line to renew the subscription to Norton Personal firewall 2003, and Norton System works 2003. I received a message to the effect that I could renew for downloads, but was no longer eligible for support. BEAR IN MIND THAT THIS WAS A TWO YEAR OLD PROGRAM. I have removed all traces of Symantec from my computer. I have now installed Nod 32 AV program. You can sign up for anything up to five years subscription. There is a national rate telephone support line in Bournemouth, as well as e-mail support. The support staff are VERY helpful. As long as you have a paid for subscription, ALL updates are included as is this support. I was even told that an update due sometime late next year would include a new firewall, and that this would be included at NO extra charge. Meantime they recommended that I install Sygate Personal firewall. This too is a good program. Symantec can go and jump in the cut as far as I am concerned. Nod is a paid for AV program, but has one of the BEST records of all AV programs, and with this kind of support is well worth the money.