Please refer Microsoft URL
This default was implemented to prevent misuse, but can be overridden by an administrator by making a change to an object in Active Directory.
Note that users in the Administrators or Domain Administrators groups, and those users who have delegated permissions on containers in Active Directory to create and delete computer accounts, are not restricted by this limitation.
To modify Active Directory to allow more (or fewer) machine accounts on the domain, use the Adsiedit tool.
WARNING Using Adsiedit incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Adsiedit can be solved. Use Adsiedit at your own risk.
- Install the Windows Support tools if they have not already been installed. This is necessary only for Windows 2000 and Windows Server 2003. For Windows Server 2008 and Windows Server 2008 R2, Adsiedit is installed automatically when you install the Active Directory Domain Services role.
- Run Adsiedit.msc as an administrator of the domain. Expand the Domain NC node. This node contains an object that begins with “DC=” and reflects the correct domain name. Right-click this object, and then click Properties.
- In the Select which properties to view box, click Both. In the Select a property to view box, click ms-DS-MachineAccountQuota.
- In the Edit Attribute box, type the number of workstations that you want users to be able to maintain concurrently.
- Click Set, and then click OK.