I 'm running Norton Security Suite on Windows 10 (on a 5 year old PC). A few days ago, I ran Windows Updates, and on rebooting, to my surprise, Windows Defender started running, and between that and Norton, brought my PC to its knees. I finally got Windows Defender stopped, and put back to bed again, but it wasn't easy -- everything was so slow and locking up. Be careful out there. BTW, I did the same update on my (new) laptop, and did not experience similar problems on it.