WINDOWS Anniversary upgrade problem

After having installed the upgrade, I was asked for Pin code or Microsoft account password.
None of my formerly used pin code or password is accepted.
I tried changing Microsoft account password on my laptop. Did not help.
What can I do to start my computer?

Option 4 here:
Administrator account - Enable or Disable in Windows 10 - Windows 10 Forums

Then once you get into the built in administrator account, you can reset your user account password. I would recommend running:
netplwiz

for that.