just trying the microsoft one now
is this the defender one,if so its basic,so if you dont do a lot of internet searching its ok.
AVG i thought was terrible
Anti-malawarebytes is very good for doing a sweep and getting rid of existing problems and its free to download with updates
i have norton 2013 and find its very good not had any problems
also you may want to go in to settings and adjust the internet security setting to medium or high,if its not allready