Depending upon how much work you want to do, it may be worthwhile having a look at the Offline NT Password and Registry Editor - This is a Linux book disk image which includes utilities to extract and update information from the Windows NT/2000 SAM database. If you are looking at following the same path for SAM database access and registry editing as what is employed by this utility, make sure that you also look closely at the information regarding NTFS checks following writing, as failure to do so can result in corruption of the file system.

Also too, this link off the same page may be helpful if you are looking at implementing a solution de novo.