"Propriétaire" is "owner", it is not "administrateur" nor "administrator". That is the account that is created aside "administrator" to be used as normal account (with administrator's rights). I'm not sure it's a bug or a feature, but XP Home unattended always creates that account, (or maybe only when you skip OOBE), even if nLite tells you that you HAVE to create an account, even if you do it, you'll always get one more account named "owner" (or "propriétaire" here). There are other threads about that.