To be honest Nortons always lagged me out too much. While playing games it would always pop up and annoy the hell out of me. i now use a free one that doesnt take much resources at all. I also use adaware once a week etc to try and keep my machine clean.

Antivirus programs have traditionally been huge resource hogs. I do not run one myself. I take measures to make sure programs can not illegally install themselves to begin with, then I will manually run one once in a while. All the time access is not necessary if you have a good understanding of the issues.

It's true that any antivirus scanner will slow your system down but it is necessary.
I use Kaspersy for Anti-Virus and Spybot Search and Destroy for Spyware.

I would never want to run my machine without some form of anti-virus software... Viruses can render the machine unusable for a while, and that would really suck! I've often used Norton, but right now I'm using AVG free, it works quite well, and it doesn't take up a lot of resources.

Apart from Norton Antivirus, even MCAfee is a trusted antivirus...Also, another contention for the antivirus software is AVG. Each of these softwares has its own pros and cons....it all depends on which one satisfies your requirements and basically, which of it protects your comp to max limit..