I was previously using free AVG, but it was annoying because of the constant tricky popups trying to sign you up for the pay version. And it seemed to be constantly failing to update automatically, and I would have to update manually.
I have switched to
Microsoft Security Essentials, which has been very easy to install and use, and is free. No nagging to upgrade to the pay version. Auto update and scans seem to be quite fast. I am hopeful that Microsoft, at least, will be able to develop a anti-virus/anti-spyware product that won't conflict with other programs.
