On Windows 2003 Server machine domain controller group policy editor can be opened as follows.
Log in to the Domain Controller machine.
Click on Start button
Select Administrative tools
Double click Active directory users and computers
This will open a console. In the left side pane, you can see a node with the domain name. Right click on it and then click on properties. Now it will open a new window on which we need to select the “Group policy” tab. Now select the appropriate group policy object in the list and then click on ‘edit’. Now this will open group policy object editor.