You can easily select all computers of a Domain by checking them in the Computer Browser. Then if you want, you can secondly uncheck non-needed computers.
Computers can be retrieved from:
From Microsoft network browser. In this case only online computers are available for selection.
From Domain controller. In this case the list is based on the computers account in each Windows Domain. So you will even see unavailable computers.
From the Global
catalog. All computers stored in Active
Directory are listed with their tree.
RemoteExec retrieves the list
of computers just when he starts. If the scan is not already complete
when the browser dialog is displayed, you will see Currently
searching in the windows title.