Norton was good when it was Norton. I recently bought copies of it and had to remove it. It took over half my system resources, ran a scan on every startup, I'd turn off the auto-updates and it would re-enable them on every startup. This was with virus scan installed only.
I had good luck with McAfee for the year that I used it. I only ran the virus scan though.
I currently run CA's virus scan that TimeWarner gives away with RoadRunner. It has been one of the best that I've run. Takes little resources, asks if updates can run, and never know it's there unless I come across a virus.
I also run spybot once in a while and rarely open attachments from anyone that I haven't verified with (depends on type). I do the windows updates, but always roll back if I see any weird stuff happening (couldn't do this with SP2 unfortunately...talk about a resource hog).
P.S. Kids don't use my work computer. Setup an account on another desktop for them that is limited, and the daughter has a mac..so not many worries there.