Windows 10 error 0x80070780 on file delete

I have been locked out from my Windows 10 account. I created a dummy account for Microsoft and now I'm locked out of Windows 10.

I've installed Windows 7 along with Windows 10 to regain control of Windows 10.
I have also tried to regain control of Windows 10 by searching different forums for answers. I've decided to try to delete 'sethc.exe' and replace it with 'cmd' in order to create a new account on Windows 10.

However when I try to delete it i get the following error message:

How can i delete 'sethc.exe' ? or How can i get back into my windows 10 ?

Assuming that the account you use to log in to the machine is a 'Microsoft' account.

• Sign in to your Microsoft account, and then select Security.

• Select Change password. Enter your current password, then the new
  password you want, and then enter the new password again.

• Select Save.

(taken directly from :- https://support.microsoft.com/en-gb/instantanswers/24749d13-a7ec-4aa7-a067-9fc74c16d8d2/to-change-your-microsoft-account-password)