I've been using Windows 10 for a while now. Recently, I've done fresh updates, which eventually created windows.old folder.
The problem started when I logged in as Administrator, and removed existing user account. I can't create back another user account.
From Control Panel -> User Accounts -> Manage another account -> Manage Accounts -> Add a new user in PC settings, opens up Settings screen.
From there, I click "Add someone else to this PC" and it results in following screen:

True that I have Windows 10 Home edition, but this was never problem.
Does any one have any clue?