"Computer <name> is already in use" error message when you add user names in Windows 2000 or Windows Server 2003

When you attempt to add users or computers, you may receive an error message that is similar to the following error message:

You may also receive the following error message when you try to setup a trust relationship in Microsoft Windows Server 2003:

This issue can occur because several user, computer, and trust relationship names that are used in earlier versions of Windows are restricted in the versions of Windows that are listed in the "Applies to" section of this article.

Restricted User Names

• Null SID
• Everyone
• Local
• Creator owner
• Creator group
• NT pseudo domain
• NT authority
• Dialup
• Network
• Batch
• Interactive
• Service
• Builtin
• System
• Anonymous Logon
• Creator owner server
• Creator group server
• Enterprise domain controllers
• Self
• Authenticated Users
• Restricted
• Terminal server user
• Proxy

Restricted Computer or Trust Relationship Names

• Internet$

Computer names and trust relationships are special cases. The versions of Windows that are listed in the "Applies to" section of this article automatically append a dollar sign ($) to the end of these accounts. Therefore, you cannot create a computer account or trust relationship that has the name "Internet." If you need to set up a trust relationship, do not use "Internet" as a domain name.