Connect your computer to a domain on Windows 7

1. Open System by clicking the Start button , right-clicking Computer, and then clicking Properties.
2. Under Computer name, domain, and workgroup settings, click Change settings.  If you’re prompted for an administrator password or confirmation, type the password or provide confirmation.
3. Click the Computer Name tab, and then click Change. Alternatively, click Network ID to use the Join a Domain or Workgroup wizard to automate the process of connecting to a domain and creating a domain user account on your computer.
4. Under Member of, click Domain.

The Computer Name/Domain Changes dialog box

1. 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.

Cr. http://windows.microsoft.com/