|You have to demote the server while it was on the domain because I am guessing that this was not the primary Domain Controller. You use DCPROMO to demote it. |
If you can't put it back on the domain then you may have to reinstall Windows Server back on it or if they have VPN at the primary office I would establish a VPN tunnel so that the server can get back on the domain so you can demote it. Was this box also a File Server?
You really should post this in one of the Windows Server forums and I highly recommend you get some one who setup the domain to help you move servers be fore you do.