What anti-virus application or security suite is installed and is your subscription current? What anti-spyware applications (other than Defender)? What third-party firewall (if any)?
Has a(another) Norton or McAfee application ever been installed on the computer (e.g., a free-trial version that came preinstalled when you bought it)?
See the "How to obtain help" section of
support.microsoft.com/kb/978207
For home users, no-charge support is available by calling 1-866-PCSAFETY (and/or 1-866-234-6020 and/or 1-800-936-5700) in the United States and in Canada or by contacting your local Microsoft subsidiary. There is no-charge for support calls that are associated with security updates. When you call, clearly state that your problem is related to a Security Update and cite the update's KB number (e.g., KB978207).
Or you can...
Start a free Windows Update support incident request:
support.microsoft.com/oas/default.aspx?gprid=6527
The Consumer Security Support home page & Microsoft Update Solution Center also offer support options
consumersecuritysupport.microsoft.com/
support.microsoft.com/ph/6527#tab3