Cmd.exe (if you are hiding file extensions of known types then it might just say "cmd" and not "cmd.exe")
Right click it and choose run as administrator
At the admin command prompt type net user JohnSmith /add
then type net localgroup administrators JohnSmith /add
Restart and log in as JohnSmith
Obviously it doesn't have to be "JohnSmith". Any Tom, Dick or Sally should work fine (dealers choice).
See if your computer behaves any better using that login.