A domain is a collection of computers on a network that are administered as a unit with common rules and procedures. Each domain has a unique name. Typically domains are used for workplace networks. To connect your computer to a domain, you need to know the name of the domain and have a valid user account on the domain.
Open System by clicking the Start button , clicking Control Panel, clicking System and Maintenance, and then clicking System.
Under Computer Name, Domain, and Workgroup Settings, click Change settings.
If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
Click the Computer Name tab, and then click Change.
Under Member of, click Domain.
Type the name of the domain that you want to join, and then click OK.
You will be asked to type your user name and password for the domain.
Once you are successfully joined to the domain, you will be prompted to restart your computer. You must restart your computer before the changes take effect.
If your computer was a member of a workgroup before you joined the domain, it will be removed from the workgroup.
The Join a Domain or Workgroup wizard automates the process of connecting to a domain and creating a domain user account on your computer. To use this wizard, click the Computer Name tab, and then click Network ID.