I had Norton way back in 98-2001 and it caused trouble on every computer i had. It even let the Chernobyl virus through which totally wiped my hard drive. So changed to mcafee and it was as bad. had panda anti-virus which was free but limited then for 5 years used AVG free with no problems, now have MSE on my lappy and AVG on my design computer. I also have AVG on my phone and ive never found any problems with it