When you set up a network, Windows automatically creates a workgroup and gives it a name. You can join an existing workgroup on a network or create a new one.
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 Workgroup, and then do one of the following:
To join an existing workgroup, type the name of the workgroup that you want to join, and then click OK.
To create a new workgroup, type the name of the workgroup that you want to create, and then click OK.
If you change the name of an existing workgroup, a new workgroup will be created with that name.
If your computer was a member of a domain before you joined the workgroup, it will be removed from the domain and your computer account on that domain will be disabled.
If your network includes computers running Windows XP, you might need to change the workgroup name on those computers to match the workgroup name on the computers running this version of Windows so that you can see and connect to all computers on your network.