NT 4.0’s Registry Hives

Table A lists the standard NT 4.0 Registry hives and theircorresponding support files. The hive support files reside in the configdirectory of your NT installation. Files without extensions contain a copy ofthe hive. Files with the .log extension contain a machine-readable record of anychanges to a hive. The .sav files contain copies of the hives at the end ofSetup'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 profileinformation.

Under normal circumstances, your system will reference the files withoutextensions. When writing changes to a hive file, the system will note thechanges in the hive's log, so that it can cancel any unfinished changes in casethe hive's updating process is interrupted. If something happens to the criticalsystem hive, the . alt version replaces it during the boot process; . alt thenmakes itself the new system hive and creates another backup . alt file.