In order to carryout an offline domain join you can use the following steps using an admin account or permissions to perform domain joins etc:

Logon to Domain Controller or Server (2008 / 2008R2)

djoin /provision /domain mydomain.com /Machine WorkstationName /SaveFile C:\Off-CLI.DJoin

/domain – Specifies the name of the domain to join.
/Machine – Specifies the name of the computer that you want to join to the domain.
/SaveFile – Saves provisioning data to a file.

Logon to the client PC/Workstation/Laptop (Windows 7)

djoin /RequestODJ /Loadfile C:\OFF-CLI.Djoin /LOCALOS /WINDOWSPATH %systemroot%

/Loadfile – Specifies the output from a previous provisioning command. (Where the offline file is)
/LOCALOS – Specifies the path to the Windows directory of the offline image.
/WINDOWSPATH – Specifies the path to the Windows directory of the offline image. (who doesn’t put this on c:\??

Don’t try and run this same piece of import code for other machines. The djoin import is unique to the PC name, therefore you will create a conflict. I found this out the hard way by getting “The trust relationship between this workstation and primary domain failed.” Error. If you do get this error message simply run through “My Computer -> Properties -> “Network ID” Wizard” or remove it from the domain and rejoin.

This is a nice little method for easy domain join, although have found that even with the system added to the domain you still can’t login as a user in order to create/setup their profile, so without a fully automated install / setup process it doesn’t save much time.

Microsoft DJoin Syntax: http://goo.gl/J7vsV