If "Norton antivirus" was free i still would not use it, "Norton antivirus" slows your computer down badly and also is difficult to remove once installed. Norton virtually admit this fault by providing a help site on the web with software to remove it.
Norton is notoriously difficult to remove properly, via the usual methods, which is why they have been forced to provide the removal tool. Without reading through the thread again, I don't know if this had been suggested to you, but sorry if it wasn't.