This is the most popoluar AV-program over here. It is free for private persons, nevertheless is a professional product that is heavily used by companies. The free version in fact is the complete pro package . Sometimes up to three updates per day, very very short reaction time to new threats. The software easily beats every virus scanner I have ever tried. no need to go for norton, or any other payware, really. Year for year it wins tests and awards by magazines, testers and editors. It has proven to be completely reliable and trustworthy for me. I give it a 100% rating - and I am paranoid, concerning computer security.
http://www.free-av.com/
Replace .com with .de to go to the original German site.