Extracting Windows hashes for password cracking is pretty basic, right? If you try to copy the SAM and SYSTEM file from C:\WINDOWS\system32\config\ on a running Windows 2003 server you get an error message, saying that it’s already in use. So before you start using shadowcopies or ntbackup or any other tools, consider just copying C:\WINDOWS\repair\SAM and SYSTEM. Basically the same files, altough it seems that the repair folder is not always up to date.
Update: There is some more research going on pauldotcom.