The Windows Registry is such a creature, and while it is certainly true that you can't be too cautious when accessing and editing Registry files, there are significant advantages to learning more about them.

A general understanding of the Registry and how it works can help you identify and fix many of the problems commonly associated with its degradation, or safely navigate its contents to customize and optimize your system's performance.

The Registry's Role in Windows

The Registry is unique to Windows, and varies a bit among its different versions. The basic Registry structure common to all versions since the introduction of Windows 95 is that of a central database containing all the information a computer needs to access and manage its individual components and user accounts.

It stores the configuration data and settings for all installed hardware, the location of application data and file type definitions for all installed software, and the security information and individual application preferences for all users.

Whenever system components are removed or installed, or adjustments are made to Control Panel settings and Windows System Policies, these changes are reflected in the Windows Registry.

Registry Storage and Structure

Much of the information contained in the Registry is stored on the computer's hard drive as a set of binary data files, strangely and appropriately named "hives".

The hives are permanent Registry components, serving as both supporting files from which Windows retrieves Registry data during system startup, and as backup files that the Registry writes to each time its supporting data is altered or changed.

Although you can't open up the hive files directly, you can see the data stored inside them by opening up the Registry itself with a Registry Editor utility like REGEDIT.EXE or REGEDT32.exe.

These utilities display the Registry's contents within a hierarchical structure of keys and subkeys, analogous to the directories and subdirectories you see in Windows Explorer.

At the top of this tree-like structure are the root keys, whose labels begin with "HKEY_". Each of these root keys branches out, first into keys and then further into subkeys. At the end of these branches of keys and subkeys lay the Registry data, or value entries, corresponding to the data stored in the hive files.

Applications, INI Files, and the Registry

Applications can interact with the Registry in many ways. They can open and close existing keys, create new keys, and delete old keys in order to retrieve, add, change, or remove data from the Registry. In short, they can store all the information they need to launch and run within the centralized, hierarchical structure of the Registry.

Before the Windows Registry was introduced, applications looked to INI files to find the configuration information, user passwords and settings, and data paths required for their execution. Because INI files are simple text files, they can't organize their data hierarchically and must be read line-by-line for their data to be accessed.

As text files they are also easier to access and edit than the Registry's hive files or the Registry itself, but are more difficult and time-consuming to find, since they are generally stored in the folders of their associated applications.

With the introduction of Windows 95, the Registry replaced most of the text-based .INI files (including WIN.INI) that were used in Windows 3.x. The idea behind the Registry was to allow multiple applications to store the data needed for their execution in a single central location, with the binary hive files and hierarchical structure making the Registry more compact and easier to navigate.