You cannot associate the built-in Administrator account with a Microsoft Account. So whatever account you used wasn’t the built-in account. The built-in account cannot be deleted, it can only be, disabled

It IS the default Administrator account. I had issued the command "net user Administrator /active:no" and this account disappeared. I quickly made it active again. And the account name (login name) is no longer Administrator. It is my hotmail account name.

In "local users and groups" (lusrmgr.msc), the first item is: Administrator, full name: my hotmail name, description: built-in account for administering the computer/domain. This is enough to remove any doubts that this is not the default Administrator account. IT IS.

And, as I have said before, when I issued the command "net user Administrator /active:no", this account DISAPPEARED from the login menu.

No. The device is not listed. I went to my Microsoft account and it reported no device found. The name Administrator no longer shows on the login screen. The login screen shows two user names, one being my Microsoft account name, and another user name. Screenshot is here:link

I suggest clicking on the "Manage my Microsoft account" though

I now have to enter my hotmail account password in order to login the Administrator account, whose account name is now my hotmail account name, not "Administrator" anymore. If it is not linked, where and how did it get my hotmail account name?

What can I do with "manage my Microsoft account"? I did click on it several times and saw my hotmail account with an option, among others, to "add device". I did not want to add device. I want to unlink the Microsoft account.

On Settings/Update & Security/Activation, it reads "Windows is activated with a digital license linked to your Microsoft account." I have provided enough proofs that this built-in Administrator account is linked to a Microsoft account. If you believe otherwise, you need to explain all the proofs I have provided so far, not just saying "if the device was linked, then it would have shown up in your devices." That statement might be true 99.9999% of the time, but who says it is true 100.0000% of the time? It is certainly not true in my case.

Your question does not contain the information required to answer your question. I have deleted my comments. You know what information should be included. When you include that information in the body of your question, I will answer your question, and reverse me downvote.

I investigated this issue for almost 4 hours this morning. Within a 1709 VM, I was able to log into my Microsoft Account through the Windows Store application (on the built-in account). I was able to log into my account with OneDrive and other applications. However, an option to link my Microsoft account was not present. I was only able to link my account, and have it show up in my Microsoft Account as a device when I created a local user.

I also spent a significant amount of time, trying ways to delete the account, I determined and verified existing documentation this wasn't possible. I will eventually migrate my research to a discussion room unless this question is updated, I can't submit an answer.

The following link describes how to delete the built-in Administrator account. I did not try it though. ("https://www.top-password.com/knowledge/delete-windows-built-in-administrator.h‌​tml")