To change the Domain Name System (DNS) suffix of your computer
You must be logged on as an administrator or a member of the Administrators group in order to complete this procedure. If your computer is connected to a network, network policy settings may also prevent you from completing this procedure.
Open System in Control Panel.
On the Computer Name tab, click Change.
Under Primary DNS suffix of this computer, type the DNS suffix you want to use.
If you want your computer to automatically update the DNS suffix if you become a member of a different Windows domain, select the Change primary DNS suffix when domain membership changes check box.
To open System, click Start, click Control Panel, click Performance and Maintenance, and then click System.
The default setting for the local primary DNS suffix is the same as the Active Directory domain name. Changing the DNS suffix will not affect your domain membership, but it could prevent other users from finding your computer on the network. If you make the primary DNS suffix of the computer different from the Active Directory domain name, the domain administrator must enable registration of the new full computer name in the Active Directory domain.
A full computer name, which includes the computer name and the primary DNS suffix, can be as long as 255 bytes, including periods.
If you switch to a new Windows secure domain and select the Change primary DNS suffix when domain membership changes check box, the DNS suffix is updated to show a new DNS suffix that matches the new Windows secure domain you are joining. For example, if you create a DNS suffix called MyMachine for membership in your current domain and join a new Windows secure domain called example.microsoft.com, then the new DNS suffix, (example.microsoft.com), is displayed under Primary DNS suffix of this computer. This new DNS suffix replaces the previous name (MyMachine) you created for membership under your old domain.
If this computer belongs to a group with Group Policy enabled on Primary DNS suffix of this computer, the string specified in Group Policy is used as the primary DNS suffix and you might need to restart your computer to view the correct setting. The local setting is used only if Group Policy is disabled or unspecified. For more information about Group Policy, click Related Topics.
When the computer is joined to a domain, you must restart the computer twice for the policy setting to take effect. After the computer is restarted the first time, the policy settings are copied to the computer from the domain. When the computer is restarted the second time, the policy settings take effect.