Norton? Bah! Gimme AVG.
I had it some years ago. "Upgraded" it and lost my internet connection. Eventually discovered that the upgrade made it incompatible with my old Win98. Nortons recommended fix was to change my O/S, & Microsoft recommended removing Norton. I followed the latter advice.
My current PC came with another AV pre-installed, which seemed fine for a while, then one day, after it had downloaded an update, it started blocking my internet connection. I reversed the update, & it worked - but wouldn't update its virus database unless I re-installed the update.. Their helpdesk wanted me to do about half a days work collecting evidence before they'd even look at the problem. At any reasonable valuation of my time, I was better off buying something else, so I told them that (they didn't seem to get it) - and while considering what to buy, I installed AVG, on the reccomendation of a friend. Still using it. I occasionally scan my PC with it & other tools, but so far, I've found only the viruses (3 last time) it's caught & quarantined. No false positives, no sign of it clagging up the PC, & nothing has got past it yet.
AVG? I love it.