On November 3 2009, Sysinternals retired NewSID, a utility that changes a computers machine Security Identifier (machine SID). I wrote NewSID in 1997 (its original name was NTSID) because the only tool available at the time for changing machine SIDs was the Microsoft Sysprep tool, and Sysprep doesn’t support changing the SIDs of computers that have applications installed. A machine SID is a unique identifier generated by Windows Setup that Windows uses as the basis for the SIDs for administrator-defined local accounts and groups.
Link http://blogs.technet.com/markrussinovich/archive/2009/11/03/3291024.aspx
