I'm Calling From Microsoft

You get a call from "someone from Microsoft" who claims they have received a notification from your computer that it has a virus, and they will help you fix it.  Microsoft will never call you, and does not track whether or not your computer has a virus.  The person on the phone may direct you to a file on your computer that shows errors "proving" what they say is true.  This is normal - every computer has errors that get logged in this file, but they do not affect your computer.