You try to add a new user or a new object to the Active Directory directory service. However, the user or the object is not added. Additionally, you may receive any one of the following error messages:
The object username could not be created. The problem encountered was; An attempt was made to add an object to the directory with a name that is already in use.
Windows cannot create the new user object because the name username is already in use. Select another name, and try again.
Windows cannot create the specified object because: The specified user already exists.
The user logon name you have chosen is already in use in this enterprise. Choose another logon name, and then try again.
Note In these error messages, username is the name of the user or of the object that you tried to add.
This problem occurs because the user name or the object name contains diacritic marks, for example, German umlauts. A German umlaut character contains a dieresis over the base character itself, such as in the following characters:
The German umlaut characters are interpreted to be the same as their base characters. For example, the "ü" character is interpreted to be the same as the "u" character. When this problem occurs, a user who is named "Muller" cannot be created if a user who is named "Müller" already exists. Similarly, a user who is named "Meissner" cannot be created if a user who is named "Meißner" already exists.
To resolve this problem, use a different name for the user or for the object that you want to add.
This behavior is by design.
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
234051 Unable to add more than one user or object with the same name to Active Directory
Microsoft has also published rules for valid characters for various object types that further reduces the freedom of name choice.For more information, click the following article number to view the article in the Microsoft Knowledge Base:
909264 Naming conventions in Active Directory for computers, domains, sites, and OUs