Why so slow?

I bought and installed Norton security because my wife's laptop was severely infected and internet surfing was basically impossible. The problem is with Norton installed everything is excrutiatingly slow! Not only that I keep getting a popup "security Request" that is as bad as the ads were.

I'm afraid to install this on my desktop becuse it will do the same there. This is the second time I've tried NIS and I'm about ready to give it up again! In the days of Peter Norton, his utilitis were fantastic and I was an enthusiastic user but no longer.