How to Disable built-in Administrator Account in Windows 10
It is really recommended to keep built-in administrator account disabled. Because Administrator can do just about anything and have unrestricted access to the Windows 10, this account is frequently targeted by malicious users and programs. So it is a good security practice to disable Administrator account.
If for some reason, if you enabled the admin account and want to disable it now, you can do it with the following steps:
Right Click on the Windows Start Button and then choose Windows Powershell (Admin).
At the Powershell window, run the following net user command to deactivate the Administrator account.
net user Administrator /active:no
There is a GUI method as well, Open Computer Management (Right Click on the Start Button and choose Manage) and move in to the User Folder in the Local Users and Groups.
Then, right click on the Administrator account, choose properties and activate the Account is disabled checkbox.
Now malicious users will be unable to log on to your Windows 10 PC using the Administrator user account. If anyone tries to log in, following error message will be displayed: Your account has been disabled. Please see your system administrator.