Windows Registry
registry

    The database used by Microsoft Windows
   95 and later to store all sorts of configuration information
   such as which program should be used to open a .doc file,
   DLL registration information, application-specific settings
   and much more.

   The Registry is stored in .dat files, one in the user's
   profile containing their per-user settings and one in the
   Windows directory containing settings that are global to all
   users.  These are loaded into memory at login.

   The loaded data appears as a tree with five main branches:
   HKEY_CLASSES_ROOT, HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE,
   HKEY_USERS, HKEY_CURRENT_CONFIG.  HKEY_CLASSES_ROOT defines
   file types and actions, HKEY_CURRENT_USER is an alias for one
   of the sub-trees of HKEY_USERS and contains user settings that
   override the global defaults in HKEY_LOCAL_MACHINE.

   The branches of the tree are called "keys" and are identified
   by paths like
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion.
   Any node in the tree can have zero or more "values" which are
   actually bindings of a name and a value, e.g. "Logon User
   Name" = "Denis".  The value can be of type string, binary,
   dword (long integer), multi-string value or expandable string
   value.

   Windows includes a Registry Editor (regedit.exe).

   (2008-01-20)