You must be an administrator to create new User account on domain based Windows 7 computer.
Go to Start Menu and type mmc, press Enter.
This will open Microsoft Management Console.
If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
In the left pane of Microsoft Management Console, click Local Users and Groups.
Click the Users folder.
Click Action, and then click New User.
Type the appropriate information in the dialog box, and then click Create.
When you are finished creating user accounts, click Close.
Thats it..
to create a windows domain you need an active directory domain controller.
then you can join your workstation to this domain. (REQUIRES WIN 7 PRO or ULTIMATE)