a program called PC-cillin internet security from Trend Micro

http://www.trendmicro.com/en/home/us/personal.htm

I have used this program for 2 years now and it is great. It scans your system for everything in real time and doesn't use as many system resources as Norton. It even protects your wireless network and more.

There is a free trial so I would recommend giving it a try (I am sure you will end up buying it).

Lee