Have had Microsoft Essentials and Malware Bytes on four machine in our household with no problems. the Microsoft Essentials is called something else now, both are free and are good. Had Norton, mcAfee, both slowed the computers down a lot. Also had problems getting Norton off two of our machines. Had to wipe the drive and start over....never Norton again. I had heard that AVG is good, but I'm not messing with anything unless I have issues....The free versions of Essentials now Windows Defender and Malware Bytes does the job.