defaultUser0 is used by windows for the OOBE if you don't delete it along with the registry keys it will just boot back to the OOBE again. defaultUser0 gets removed by the OOBE after setup leaving your system vulnerable. The administrator account is a built in account that is disabled by default but won't be disabled if you completely bypass the OOBE or don't use the old local account setup which you no longer can do because of microsofts removal of the feature.