Documentation :

https://fr.wikipedia.org/wiki/Base_de_registre

http://msdn.microsoft.com/fr-fr/library/cc759303%28v=ws.10%29.aspx

The system registry resides in several files. There are two registry files in old Windows 95/98/Me : system.dat and user.dat. User.dat contains the HKEY_CURRENT_USER registry hive while system.dat contains all other hives. Both these files can be found in the Windows directory.

Newer Windows versions (NT/2000/XP/2003/2008/Vista/Win7) the system registry resides in the following files (in C:WindowsSystem32config):

NTUSER.DAT - this file contains the HKEY_CURRENT_USER hive. Normally the NTUSER file has a 'hidden' attribute and therefore is invisible in Explorer. This file is located in the user profile folder.

All the following files are located in %SysRoot%\System32\config folder:

SAM. - this file contains the HKEY_LOCAL_MACHIVE\SAM hive

SOFTWARE.  this file contains the HKEY_LOCAL_MACHIVE\SOFTWARE hive

SECURITY. this file contains the HKEY_LOCAL_MACHIVE\SECURITY hive

COMPONENTS. - this file contains the HKEY_LOCAL_MACHIVE\COMPONENTS hive (optional)

BCD-TEMPLATE - this file contains the HKEY_LOCAL_MACHINE\BCD00000000 hive (optional)

SYSTEM. this file contains all other keys of HKEY_LOCAL_MACHIVE (such as SYSTEM)