Einfach:
Bei wenigen Benutzern per Hand durch drücken von F2 bei marikiertem Benutzernamen in der MMC "Active Direcory Benutzer und Computer", dann ensprechend ändern und nach drücken auf ENTER auch den Anzeigenamen ändern.

Eleganter wie folgt:
XADM: How to Change Display Names of Active Directory Users
The information in this article applies to:
Microsoft Exchange 2000 Server
This article was previously published under Q250455
SUMMARY
When a new user is created in Active Directory, the Full name field is always generated in FirstName LastName format. In turn, this field sets the Display Name field on creation, therefore, you end up with a FirstName LastName formatted global address list.

You can make this change by using the Adsiedit utility. Adsiedit not only changes the default way the Display Name field is built, but also the Full Name (that is, the "cn") field, therefore, users appear in the chosen format when you look in the Users and Computers snap-in.
MORE INFORMATION
ADSIEdit Instructions
WARNING: If you use the ADSI Edit snap-in, the LDP utility, or any other LDAP version 3 client, and you incorrectly modify the attributes of Active Directory objects, you can cause serious problems. These problems may require you to reinstall Microsoft Windows 2000 Server, Microsoft Exchange 2000 Server, or both. Microsoft cannot guarantee that problems that occur if you incorrectly modify Active Directory object attributes can be solved. Modify these attributes at your own risk.
Insert your Windows 2000 Server CD.
Navigate to the \support\tools directory.
Double-click on the Support.cab file.
Locate the files adsiedit.msc and adsiedit.dll. Extract them to your %systemroot%\system32 directory.
Run regsvr32 adsiedit.dll.
Start Microsoft Management Console (MMC), and then add the ADSI Edit snap-in.
Right-click the top node, and then click Connect to.
Change the Naming Context to "Configuration Container," and then click OK to bind and authenticate.
Expand the Configuration Container node, and then expand the Configuration node.
Expand the cn=DisplaySpecifiers node, and then double-click CN=409.NOTE: 409 is the Locale ID for U.S. English. If you are in a multi-lingual environment, you may need to make changes to the other codes. Most of the Asian codes are already set.

The International Telecommunication Union (ITU) and International Organization for Standardization (ISO) define the code pages. Some information can be found at:
http://www.itu.int/ITU-T/bulletin/codes.html
or at the ITU or ISO home pages:
http://www.itu.int/home/index.html
http://www.iso.ch/

For additional information about supporting localized Exchange Clients, click the article number below to view the article in the Microsoft Knowledge Base:

150977 XADM: Supporting Localized Exchange Clients
In the right-hand pane, open the properties for "CN=user-Display".
Scroll to the createDialog optional property.
Set the attribute to "%<sn>, %<givenName>" . Ensure that you click the "Set" button.

NOTE: You can use any LDAP attribute name that appears on the Creation dialog box; the other obvious attribute is %<initials>.
Click OK to close the dialog box.
In Active Directory Users and Computers, create a new User; the Full Name (and thus, the Display Name) are built in accordance with your rule.
Making these changes can have adverse effects. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

276266 Group Changes for Users with LDAP-Restricted Characters

For additional information about how to use an ADSI script to perform this task, click the article number below to view the article in the Microsoft Knowledge Base:

277717 How to Change the Display Names of Active Directory Users with Active Directory Services Interface Script

Oder noch eleganter per Skript:
XADM: How to Change Display Names of Active Directory Users:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q250455

Fuer bestehende user:
How to Change Active Directory Display Names:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q300427

Change Display Names of Active Directory Users with ADSI Script:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q277717

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