I'm one who believes in preventative medicine, and therefore attempt to keep my applications updated with the most secure versions as identified by the Secunia Personal Software Inspector. (free for home use)

For the O/S -- all my machines run either XP Home or XP Pro -- I allow automatic download, but I install them at a time of my choosing, usually after consulting the Window Secrets newsletter, run by Brian Livingston, with longtime PC guru, Fred Langa. They evaluate and report on the efficacy of all of the MS patches, and occasionally issue a warning when a patch doesn't do what's intended, or can be damaging to your machine.

Had Norton installed on one machine many years ago, but became disenchanted watching it grow into machine-clogging bloatware, and ditched it after paying for only one year subscription update. (Got a rebate on the original deal, bringing the purchase cost down to -$.01...) Since then, I've mainly used AVG Free, although there have been rough spots with it, especially with the original update to version 8.

I've read positive reports of the new MS Security Essentials in Windows Secrets and several other sources, and have loaded that on several machines, replacing AVG, which has been bugging users to move up to their version 9. I was already annoyed at the number of processes spawned by AVG, and decided that this was a good time to switch, rather than updating to AVG 9. So far, Security Essentials has been a winner for me -- it seems to be less pervasive than AVG was.

For web browsing, I use Firefox except when checking Windows Update, which requires IE or, at minimum, the IE engine running in Firefox. I leave it basically fully-enabled, because I don't want my browsing experience to be inhibited by paranoia over being infected by a website. I don't visit the kind of sites that are most likely to have malware waiting to jump into my system, and rely on the resident anti-malware capability along with a fair amount of computer, internet & security savvy to prevent problems.

The combination of all of these steps has been very successful over the years, as I've not once suffered from malware damage or had to reload the O/S because of some suspected virus damage.

I also work on a lot of systems for friends & families who have 'slow computer complaints', and have found that my most valuable piece of Norton software is, unfortunately, the Norton Removal Tool. You also need to check for multiple antivirus, antispyware tools and firewalls, which can conflict with each other and tie up enormous amounts of system resources.