If you just want to regain access to the files on your computer, you can bypass the Microsoft account login with PCUnlocker, Kon Boot, Elcomsoft or Passware Kit. Another way is to create a new admin...

If you get "access denied" error, it's possible that your main account is a standard user, not administrator.

Is that folder in your system partition? If you're logged in as administrator account and couldn't open that folder, check if there is any folder protection software installed on your computer.

You need to take ownership of your old user profile directory before deleting it. You can use the free softwares TakeOwnershipPro or TakeOwnershipEx suggested by NavyLCDR.

Hi stocktiki! The child account is also a standard local account and you can remove it from Control Panel.
User Account - Delete in Windows 10 - Windows 10 Forums

I also have the same problem with child account. When the child account is switched to a local one, all my blocked websites and programs become accessible again. This should be a serious bug in...