NewSid is officially not supported by Microsoft anymore. There are chances where you get stuck up during cloning, have multiple machines with same SID. How do you find the existing SID? Its simple. This can be achieved using free tool from Sysinternals called PsGetSid.

First you have to download PsGetSid from PsGetSid download page. Then extract it from the archive PsTools on your machine. You should see PsGetSid among the exe files available in the folder.

Execute the command PsGetSid and you should get the output.

Utility download link:
http://technet.microsoft.com/en-us/sysinternals/bb897417.aspx

Thanks,
WintelAdmin