You are probably reading this page because you are contemplating a Windows XP Registry fix after experiencing or suspecting a problem with your Windows Registry. Common symptoms are lengthy program loads and erratic behaviour by application programs such as MS Windows Explorer.

Before attempting a Windows XP Registry fix, using the Windows Registry editor, you want to ensure that you have a good understanding of the structure of the Registry.

The Windows Registry replaces most of the text-based .ini files that were used in Windows 3.x and MS-DOS configuration files, such as the Autoexec.bat and Config.sys.

The Windows XP Registry is the database in which the operating system stores most of its settings as well as the settings for application programs. In addition, it contains information about the hardware configuration of the system and the start-up procedure. It also defines relationships between different parts of the operating system's user interface. For example, the Registry defines the appearance of the desktop and the behaviour of the Start menu and Taskbar.

The Registry contains two basic elements, keys and values, and Windows stores the entire contents of the Registry in two files: System.dat and User.dat. These are binary files that cannot be viewed with a text editor, as is the case with .ini files. For protection, Windows also turns on the read-only, system, and hidden attributes of the System.dat and User.dat files so the user won't accidentally replace, change, or delete them. System.dat contains computer-specific configuration data, and User.dat contains user-specific data.

The Registry is split into a number of logical sections, or "Hives”. Hives are generally named by their Windows API definitions, which all begin with "HKEY" and to Programmers, are known as a handle to a key. Registry Keys are similar to folders - in addition to values, each key can contain subkeys, which may contain further subkeys, and so on.

HKEY_CLASSES_ROOT - Points to branch of Hkey_Local_Machine that describes certain software settings.

HKEY_CURRENT_USER - Points to a branch of Hkey_Users for the user who is currently logged on.

HKEY_LOCAL_MACHINE - Contains computer-specific information about the type of hardware installed, software settings, and other information. This information is used for all users who log on to this computer.

HKEY_USERS - Contains information about all the users who log on to the computer, including both generic and user-specific information. The generic settings are available to all users who log on to the computer. The information is made up of default settings for applications, desktop configurations, and so on. This key contains sub keys for each user that logs on to this computer.

HKEY_CURRENT_CONFIG - Points to a branch of Hkey_Local_Machine\Config that contains information about the current configuration of hardware attached to the computer.

HKEY_DYN_DATA - Points to a branch of Hkey_Local_Machine that contains the dynamic status information for various devices as part of the Plug and Play information.

Keys are referenced with syntax similar to Windows' path names, using backslashes to indicate levels of hierarchy. E.g. HKEY_LOCAL_MACHINE\Software\Microsoft\Windows refers to the subkey "Windows" of the subkey "Microsoft" of the subkey "Software" of the HKEY_LOCAL_MACHINE key. They are abbreviated to a three or four letter short name starting with "HK" (e.g. HKCU and HKLM). Each key is associated with a value entry. Value entries are analogous to files in Windows Explorer.

The HKEY_LOCAL_MACHINE (local machine-specific configuration data) and HKEY_CURRENT_USER (user-specific configuration data) nodes have a similar structure to each other. User applications will typically look up their settings by first checking for them under the User key and, if not found, will then look under the Local Machine key.

The Registry in 64-bit versions of Windows XP, Windows Server 2003, and Windows Vista is divided into 32-bit and 64-bit keys. Many of the 32-bit keys have the same names as their 64-bit counterparts, and vice versa. The 64-bit version of the Windows Registry Editor that is included with these operating systems distinguishes between them by displaying them under different node names within the key name.

Unfortunately one cannot ignore the fact that the Registry can be a complicated and intimidating subject for the non-technical user. It may therefore be advisable to take a look at our Registry cleaner reviews to assist you in selecting the best Registry cleaner, which will automatically take care of all the intricacies of your Registry.