WARNING! Be careful when running this script. It will actually shut down all Computers in your Domain
Dim ComputerOp As IADsComputerOperations
Dim NameSpace As IADsContainer
Dim Computer As IADsComputer
Dim DomainContainer As IADsContainer
Dim Domain As IADsDomain
'Bind to the known Namespace.
Set NameSpace = GetObject("NTDS://")
'Enumerate the all domains first
For Each Domain In NameSpace
Set DomainContainer = Domain
DomainContainer.Filter = "Computer"
'Enumerate the all Computers in the Domain
For Each Computer In DomainContainer
get the IADsComputerOperations interface
Set ComputerOp = Computer
'Call Shutdown method of IADsComputerOperations
ComputerOp.ShutDown True 'True means reboot
Next Computer
Next Domain