I have been conducting extensive research over the past few years and, by using the medium of pornography, can conclude that AVG free has maintained the integrity of my machine despite rigourous (and sometimes ruthless0 "testing".
Any time I used Norton I ran into snags within a few months of the renwal date. I followed the removal advice that has been given already.
AVG free, CCleaner and superantispyware. Advance system care as well.
Or go Linux Ubuntu?!