Lol,i would wanna multi-quote all of you,but i didn't.So,I'll explain something.Norton is a piece of shi*.AVG is way better than that,And Kaspersky Internet Security is the best.Oh,and BTW,check the file called csrss.exe.I had a virus from this,but KIS detected it in time and i deleted it.You can see it from the registry,or from Windows Task Manager under Processes.
This thing (csrss.exe) always played a popup or a youtube video.