My first thought was to use MacroMaker to launch a numlock VBScript every few minutes. While I was getting that set up, I ran across a setting in MacroMaker that provided for this feature. But on the problem system, it would manipulate the CapsLock and ScrollLock, but nothing I tried would touch the NumLock. Very frustrating.

NumLock ON VBScript:
set WshShell = CreateObject("WScript.Shell")
WshShell.SendKeys "{NUMLOCK}"

Registry settings:
HKEY_CURRENT_USER\Control Panel\Keyboard
HKEY_USERS\.DEFAULT\Control Panel\Keyboard

for the Key and value:
"InitialKeyboardIndicators" = "2"

original document