I have used Norton Antivirus for many years and have been happy with it. A couple of years ago, I tried their integrated secruity system because Fry's Electronics has a "free with rebate" offer on it (they still do). However, it is so complex and hard to understand that I gave up on it last year. It also slowed things down.
Am back to Norton Antivirus only and very pleased. If you purchase the prior years version, you can get it for only $5-10 a year with all the same virus updates that the latest version offers. There is also a 3-pack version that is installable on up to three of your pc's. All installs expire 12 months after the FIRST install, though.