Table A lists the standard NT 4.0 Registry hives and their corresponding support files. The hive support files reside in the \config directory of your NT installation. Files without extensions contain a copy of the hive. Files with the .log extension contain a machine-readable record of any changes to a hive. The .sav files contain copies of the hives at the end of Setup's text-mode step. The .alt file contains the Last Known Good information, in case anything happens to the system hive. The .dat files contain user profile information.

Under normal circumstances, your system will reference the files without extensions. When writing changes to a hive file, the system will note the changes in the hive's log, so that it can cancel any unfinished changes in case the hive's updating process is interrupted. If something happens to the critical system hive, the . alt version replaces it during the boot process; . alt then makes itself the new system hive and creates another backup . alt file.

TABLE A: The Standard NT 4.0 Hives
Hive Name Hive Support Files
HKEY_LOCAL_MACHINE\SAM SAM, SAM.LOG, SAM.SAV
HKEY_LOCAL_MACHINE\Security SECURITY, SECURITY.LOG, SECURITY.SAV
HKEY_LOCAL_MACHINE\Software SOFTWARE, SOFTWARE.LOG, SOFTWARE.SAV
HKEY_LOCAL_MACHINE\System SYSTEM, SYSTEM.ALT, SYSTEM.LOG, SYSTEM.SAV
HKEY_CURRENT_CONFIG SYSTEM, SYSTEM.ALT, SYSTEM.LOG, SYSTEM.SAV
HKEY_USERS\.DEFAULT DEFAULT, DEFAULT.LOG, DEFAULT.SAV
HKEY_CURRENT_USER NTUSER.DAT, NTUSER.DAT.LOG
Source: Microsoft Windows NT Workstation Resource Kit. Redmond, WA: Microsoft Press, 1996