We run into this issue when copying virtual servers. The below instructions will help you correct this issue quickly.
--------------------------- Computer Name/Domain Changes --------------------------- The following error occurred attempting to join the domain "company": The domain join cannot be completed because the SID of the domain you attempted to join was identical to the SID of this machine. This is a symptom of an improperly cloned operating system install. You should run sysprep on this machine in order to generate a new machine SID. Please see http://go.microsoft.com/fwlink/?LinkId=168895 for more information. --------------------------- OK ---------------------------
As indicated, you need to run sysprep on the machine.
c:\Windows>cd c:\windows\system32\sysprep
c:\Windows\System32\Sysprep>Sysprep /generalize /shutdown /oobe
After the above command runs the machine will reboot and you should be good to go.