What is the Registry? Part I

The Registry is a database used to store settings and options
for the 32 bit versions of Microsoft Windows including Windows 95, 98,
ME and NT/2000/XP. It contains information and settings for all the
hardware, software, users, and preferences of the PC. Whenever a user
makes changes to a Control Panel settings, or File Associations, System
Policies, or installed software, the changes are reflected and stored
in the Registry.

The physical files that make up the registry are stored
differently depending on your version of Windows; under Windows 95 & 98
it is contained in two hidden files in your Windows directory, called
USER.DAT and SYSTEM.DAT, for Windows Me there is an additional
CLASSES.DAT file, while under Windows NT/2000 the files are contained
seperately in the %SystemRoot%\System32\Config directory. You can not
edit these files directly, you must use a tool commonly known as a
"Registry Editor" to make any changes (using registry editors will be
discussed later in the article).

The Structure of The Registry

The Registry has a hierarchal structure, although it looks
complicated the structure is similar to the directory structure on your
hard disk, with Regedit being similar to Windows Explorer.

Each main branch (denoted by a folder icon in the Registry Editor, see
left) is called a Hive, and Hives contains Keys. Each key can contain
other keys (sometimes referred to as sub-keys), as well as Values. The
values contain the actual information stored in the Registry. There are
three types of values; String, Binary, and DWORD - the use of these
depends upon the context.