I have Avast! in this laptop since i bought it. I see no reason so far to replace it. Some comparatives say Antivir is better, and i don't argue with that. People who study that with a good and transparent method will know and infer a lot better than me. But the difference isn't that great, and Antivir's free version, well, it's the free version. There's one Avast! AFAIK, gets viruses and trojans, and i don't see any conflicts so far. And i don't change my AV because of 'statistically not so important' differences. Which can change in a year. Both are good enough to keep. I prefer Avast! because i already have it, it's in the top, it's free, comprehensive, and easy to use. You can't go wrong with either. If you have one of them, and you have no problems so far, don't change AV. Period.