To join a workgroup
You must be logged on as an administrator or a member of the Administrators group in order to complete this procedure. If your computer is connected to a network, network policy settings may also prevent you from completing this procedure.
Open System in Control Panel.
On the Computer Name tab, click Change.
Under Member of, click Workgroup, type the name of the workgroup that you want to join, and then click OK.
If your computer was a member of a domain before you joined the workgroup, it will be disjoined from the domain and your computer account will be disabled.
To open System, click Start, click Control Panel, click Performance and Maintenance, and then click System.
A workgroup name must not be the same as the computer name. A workgroup name can have as many as 15 characters, but it cannot contain any of the following: ; : " < > * + = \ | ? ,
If your computer is a member of a workgroup, no networking is installed, or TCP/IP is not installed, then the computer name cannot be more than 15 characters, and the characters must all be uppercase.