If you are curious about the details behind the registry key that your Antivirus program needs to create in order to receive Windows Updates, The Register describes its purpose here.  In essence, modern AV programs regularly access the kernel to look for suspicious activity and become quite upset when they are not allowed to access it after the patch places the kernel in isolation, upset enough to continually crash your computer.  Ensuring your AV software has updated itself to ensure that this does not occur before allowed the Windows patch to install is a good thing, however there is a serious problem with the way Microsoft decided to deal with the situation.  Until that key is present, you will not be able to install any new security patches; something which should be changed ASAP as it could help spread other infections simply because you had the temerity not to use Windows Defender.

"Microsoft's workaround to protect Windows computers from the Intel processor security flaw dubbed Meltdown has revealed the rootkit-like nature of modern security tools."

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