Well, I think I figured out how to do the first part (detecting this setting). It is actually in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
the key is "LimitBlankPasswordUse", if it is 1, then it is enabled, otherwise disabled.
So, a reading that, at least, will show me if I need to tell the user to change it or not. I doubt I can change it, though ...
source share