I've used Norton, McAfee and AVG. I like AVG cause it's free and does a great job. Only problem is it can hog system resources. I came across Avira Antivir and it's also free. Gets exvellent reviews but here's the sweet spot for traders - it doesn't hog system resources. I can run a scan with Ensign running whereas AVG would bring proceedings pretty well to a a halt. Hope this helps some of you.