ok,well windows defender is not all that great,but start by running a scan and see if it picks up anything.then download and run a scan with adwcleaner.delete anything it comes up with and post the log.also post the windows defender log.then download and run a scan with junkware removal tool and delete anything it comes up with.post the log from this scan as well.finally run a scan with malwarebytes and delete anything it comes up with and post the log.as far as avs go i recommend avast.
http
/www.bleepingcomputer.com/download/adwcleaner/
http
/www.bleepingcomputer.com/download/junkware-removal-tool/