Have a look at the following article. It should help you.
2.1 Installing Windows 2003 Server (first Domain Controller)
1. Log on as Administrator to the Member Server.
2. Click Start, and then click Run.
3. In the Run box, type “dcpromo” and then click OK.
4. On the Welcome to the Active Directory Installation Web page, click NEXT.
5. On the Domain Controller Type page, ensure that “New Domain Controller for a new Domain” is selected, and then click NEXT.
6. On the Domain Controller Type page, ensure that “New Domain Controller for a new Domain” is selected, and then click NEXT.
7. ON the Create or Join Forest page, ensure that “Create a new Forest of Domain trees” is selected, and then click NEXT.
8. On the New Domain Name page, in the Full DNS Name the new domain text box, type the “Domain name” you want for your Organization and then click NEXT.
9. On the NetBIOS Domain name page, ensure that “Domain Name” appears and if Domain name doesn’t appear specify the NetBIOS name of the Domain name, and then click NEXT.
10. On the database and log locations page, accept the default locations by clicking NEXT.
11. On the Shared System Volume page, accept the default location by clicking NEXT.
12. On the Permissions page, select “Permissions compatible only with Windows 2000 servers’, and then click NEXT.
13. On the Directory Services Restore Mode Administrator password page, in the password and confirm password boxes, type “password and in confirm password boxes” and then click NEXT.
14. On the Summary page, review the Options you selected and then click NEXT.
15. The Active Directory Installation begins.
16. When the completing the Active Directory Installation wizard page appears, click FINISH, and then Restart Your Computer.
2.2 Joining a Client to the Domain
1. Logon to Client System by using an Administrator Account.
2. Right click My Computer and click properties.
3. System properties dialog box appears, select the Network Identification tab, and click properties.
4. In the Identification changes Dialog box, under Member of, Select DOMAIN.
5. In the Domain box, type the Domain name you want your Organization and then click OK.
6. In the Domain user name and password dialog box, type administrator and password respectively and press ENTER.
7. Welcome Message appears indicating that the computer was successful in joining the Domain.
8. Click OK to close the Network Identification message box.
9. Click OK to close the System Properties dialog box.
10. Your Computer restarts.