Try the following procedure.
1, Press "Ctrl", "Alt" and "Del" at the same time in a sate of being Num Lock setting on,
and display "Windows Security".
2, Click "Log Off".
3, Click "Yes" in the window of "Log Off Windows".
4, Num Lock is on when you log on next time.
*Do the above procedure in a state of being Num Lock setting off, if you want to set it off when you log on.