As per Microsoft Active Directory architecture, every object (users, groups & computers) in the domain has a unique identifier, known as a SID. These SIDs are unique alphanumeric strings that correspond to a single object in the domain. When you copy a virtual machine directory, the resultant virtual machine has the same SID as the original virtual machine. When you try joining this new virtual machine to the same domain where the original virtual machine is, Active Directory sees two machines with a single SID and warns you that there is a SID conflict.
Windows SID needs to be changed after copying a virtual machine directory
To change a SID, you must use the Windows utility Sysprep (System Preparation Tool). This is the only method that is supported by Microsoft. For more information on using Sysprep, see this Microsoft article: How to Use Sysprep: An Introduction.
Note: Microsoft does not support using NewSID to change a SID. As of November 9th, 2009 NewSID is no longer available for download. For more information, see this Microsoft blog post: NewSID v4.10.
This table lists the Sysprep version for the Windows versions that are supported for Image Customization. Compare the Sysprep version number with the Windows version for which it is intended: