It's actually quite important to have antivirus software - I used AVG for a very long time on my last Win XP desktop computer. Then I got a new laptop with Win Vista, and it came with a year and a half subscription's worth of McAfree. I know that's not a very good software, but I suppose it did an okay job. Now that my license is expired, I've installed Avira on my laptop - its really good, and its very very light compared to AVG. I haven't ever used Avast, though many people say it's good. However, for me, Avira does an awesome job.