In the Workgroup or Computer Domain page, the wizard prompts you to specify whether or not you want to join an existing domain on the network or create a workgroup. If this is the first server on your network and you plan to create a domain later, or if you don’t want to use a domain at all, select the No radio button on this page and specify the name of a workgroup in the Workgroup or Computer Domain field. You must create a workgroup, even if it’s a workgroup containing one machine.
