Something to remember while giving permission to add computer to domain

The "Add workstations to domain" right gives a user the authority to add 10 new computers to the domain. After 10 workstations have been added, further attempts are denied. To give unlimited authority to add computers to the domain, grant the "Create computer object" permission on the organizational units (OUs) in which the team needs to add new computers.

 Even though the "Add workstations to domain" right shows up on Windows Server 2003 and Windows 2000 Server member servers and Windows XP computers, it takes effect only on domain controllers (DCs). Also, default settings assign this right to Authenticated Users, which means that anyone in your forest or in a trusted forest can create as many as 10 computer accounts, so one might want to disable this right.