I used Norton because it came free with my rig and then paid 19 bucks for it for a year. Then they wanted 39 bucks to renew and I wised up by reading MS help forums and cut the cord. Don't pay for security folks, it isn't worth it, but if you must, Norton did ok by me, but I never needed their support either.
I went with ZoneAlarm Free, and although it was not easy to set up (the problem was with correct settings in ZoneAlarm, not my machine). I had connectivity problems with the internet at first, but after pulling my hair out I finally saw that my ignorance with the settings was the problem.
I have had it a year and I am invisable to hackers, at least that is what all the online tests indicate. I would not be without it, although very knowledgable MS experts claim they had too many problems using it. PS: you have to turn off MS SP2 firewall to use ZoneAlarm Free.
I note that it rarely updates, but when it does... watch out. It takes a long time to download on dial up.
I would not pay for Norton or any other security software. Freeware is good enough for most folks, especially if they do not surf into dangerous waters and avoid attachments and links in their emails.