I recently was infected by a nasty virus that called itself "MS Removal Tool". It rendered all my commands unresponsive and removed the icons to my Norton anti-virus, substituting itself. I couldn't run any kind of anti-virus or anti-malware to try to isolate it and remove it. I had to take my PC to a computer hospital to have it wiped clean. If anyone else has a notice pop up on their screen saying that your system has been infected and then begins a "free" scan without your permission, close the window as soon as possible and you might avoid the inconvenience and cost that I incurred. I may have clicked on the message since it looked like a legitimate MS [Microsoft] Windows message. DON'T DO THAT !