Normaly the tool NETDOM does not exists on a Windows 7 system. Microsoft has added the powershell cmdlet “Add-Computer” instead of the tool NETDOM.
Link “Add-Computer” : [1] http://technet.microsoft.com/en-us/library/dd347556.aspx

With this powershell cmdlet it is not possible to join a Windows 7 system unattended to a Active Directory.
But … now I have found the NETDOM tool for Windows 7.

1. Download and Install the RSAT Tools for Windows 7.
Link “RSAT” : [2] http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=7d2f6ad7-656b-4313-a005-4e344e43997d

2. Open a command prompt after installing the RSAT Tools and enter the following command.

start /w pkgmgr /iu:RemoteServerAdministrationTools-Roles-AD-DS-SnapIns;RemoteServerAdministrationTools-Roles-AD-DS;RemoteServerAdministrationTools-Roles-AD;RemoteServerAdministrationTools-Roles;RemoteServerAdministrationTools

Now there is the tool NETDOM available on you Windows 7 system.