Generate New SID in Server 2012
Log on to Windows Server. Open Windows Explorer, and browse, C:\Windows\System32\Sysprep
Right-click sysprep application and click Run as Administrator.
System Preparation tool will open as shown below. Choose Enter System Out-of-Box Experience (OOBE) option, check Generalize option, choose Reboot as shutdown options and click OK.
The application will generate new SID and perform all the required actions and will reboot.
After the reboot, you will be asked to
enter the product key (optional), accept License terms, and enter new
Administrator password. You can then, login to the server and change
Host name and IP address. In this way you can generate new SID.
參考: http://www.mustbegeek.com/generate-new-sid-server-2012/