Ever since Windows 2000, by default, Numlock is turned off at the logon screen. This can be annoying if you use the numpad to type in (part of) your password. Luckily, you can change this behaviour through a registry fix.
The registry key to change is the same for all versions of Windows, but the value to enter is different depending on the version of Windows.
Fire up regedit.
Navigate to the key HKEY_USERS\.DEFAULT\Control Panel\Keyboard.
Look for the registry value InitialKeyboardIndicators, which needs to be changed to:Windows 7: set the value to 2
Windows 8, 8.1, 10 (older builds): set the value to 80000002
Windows 10 (newer builds): set the value to 2147483650