The syntax of the command is: adprep option Supported : /forestPrep Update forest information /domainPrep Update domain information ...

The syntax of the command is:

adprep  [option]

Supported :
/forestPrep               Update forest information

/domainPrep               Update domain information
                          Must be run after /forestPrep is finished

/domainPrep /gpPrep       Update permissions on Group Policy Objects in
                          Active Directory Domain Services and SYSVOL
                          Must be run on the infrastructure role master
                          Must be run after /forestPrep is finished

/rodcPrep                 Update permissions on all partitions to 
                          enable replication for Read-only Domain Controllers.
                          Runs remotely and contacts a partition replica to
                          update permissions. Must be run after /forestPrep is 
                          finished. Can be re-run at any time. You should run 
                          this in particular when you have DNS application
                          partitions in your forest.

Supported [option]:

/forest           Update the specified forest. Can be a DNS
                          forest name or a NETBIOS forest name. Default is
                          the local machine forest.

/domain           Update the specified domain. Can be a DNS
                          domain name or a NETBIOS domain name. Default is
                          the local machine domain.

/user               The name of the user to use when connecting to
                          the domain (default is current user).

/userdomain       The domain the user is a member of. Can be a DNS
                          domain name or a NETBIOS domain name.

/password [password | *]  The password of the supplied user.


/noSPWarning              Suppress the Windows Server 2003 requirement warning
                          during /forestprep.

/silent                   Suppress all output.

/forceReplicate           Replicate partitions from the schema role master if
                          /forestPrep is finished but the infrastructure role
                          master is not up-to-date

Examples:

Forestprep:
adprep /forestprep
adprep /forestprep /forest corp.contoso.com
adprep /forestprep /user administrator /userdomain headquarters.corp.contoso.com /password xyzzy
adprep /forestprep /forest corp.contoso.com /user administrator /userdomain headquarters.corp.contoso.com /password *

Domainprep:
adprep /domainprep
adprep /domainprep /domain accounting.corp.contoso.com
adprep /domainprep /user administrator /userdomain headquarters.corp.contoso.com /password xyzzy
adprep /domainprep /domain accounting.corp.contoso.com /user administrator /userdomain headquarters.corp.contoso.com /password *

Gpprep:
adprep /domainprep /gpprep
adprep /domainprep /gpprep /domain accounting.corp.contoso.com 
adprep /domainprep /gpprep /user administrator /userdomain headquarters.corp.contoso.com /password xyzzy
adprep /domainprep /gpprep /domain accounting.corp.contoso.com /user administrator /userdomain headquarters.corp.contoso.com /password *

Rodcprep:
adprep /rodcprep
adprep /rodcprep /forest corp.contoso.com
adprep /rodcprep /user administrator /userdomain headquarters.corp.contoso.com /password xyzzy
adprep /rodcprep /forest corp.contoso.com /user administrator /userdomain headquarters.corp.contoso.com /password *