You can pick several free versions and rotate them, run one one day and another the next and do better than norton. Norton was more trouble than a virus to me. Download.com the old PC magazine is the place to go. SuuperAntiSpiwarare is the one I use the most but the free one has a popup I have to x out each day. If you upgrade you only get 30 days more and they want money. They even have technical advice also.
Over the years, I have used seveal AV software.
Many of them because bloatware and took more resources, thus slowing the pc to a crawl.
Many upgrades created major conflicts with other programs.
MS Essentials seems to work seemlessly.