If you’re trying to run newsid.exe on windows vista you will most probably get an error saying that newsid.exe can’t find the computer SID. The problem can be fixed easily :
right-click on newsid.exe and select “run as administrator” 😉
If you can’t run it as an admin, launch a cmd.exe and use the runas command to get privileged access :
runas /user:domain\username newsid.exe