WARNING! There are many scams out there where someone will calls you pretending to be Microsoft or some other tech company that you have a virus and they request access to your computer. Simply deny access and hang up.
You may also receive a popup on your computer screen saying you have a virus and to call now! DO NOT call that number on your screen. Reboot your computer and you will be fine. If the message doesn't go away, call your trusted computer tech.