Using NewSID to change SID on Windows Server 2008 R2 will destroy operating system. So you should only use sysprep tool to change SID on Windows Server 2008 R2.
RUN>sysprep will take you to sysprep folder (c:\Windows\System32). Open sysprep application. Select Enter System Out-of-Box Experience (OOBE). Important: select Generalize if you want to change SID, it’s not selected by default. As Shutdown Options select Reboot.