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Registry Editor is an advanced tool for viewing and changing settings in your system registry, which contains information about how your computer runs. Windows stores its configuration information in a database (the registry) that is organized in a tree format. Although Registry Editor enables you to inspect and modify the registry, normally you do not need to do so, and making incorrect changes can break your system. An advanced user who is prepared to both edit and restore the registry can safely use Registry Editor for such tasks as eliminating duplicate entries or deleting entries for programs that have been uninstalled or deleted.
Folders represent keys in the registry and are shown in the navigation area on the left side of the Registry Editor window. In the topic area on the right, the entries in a key are displayed. When you double-click a entry, it opens an editing dialog box.
You should not edit your registry unless it is absolutely necessary. If there is an error in your registry, your computer may not function properly. If this happens, you can restore the registry to the same version you were using when you last successfully started your computer. For instructions, see Related Topics.
Registry Editor Keys

The navigation area of the Registry Editor displays folders, each of which represents a predefined key on the local computer. When accessing the registry of a remote computer, only two predefined keys, HKEY_USERS and HKEY_LOCAL_MACHINE, appear.
Folder/predefined key Description
HKEY_CURRENT_USER Contains the root of the configuration information for the user who is currently logged on. The user's folders, screen colors, and Control Panel settings are stored here. This information is referred to as a user's profile.
HKEY_USERS Contains the root of all user profiles on the computer. HKEY_CURRENT_USER is a subkey of HKEY_USERS.
HKEY_LOCAL_MACHINE Contains configuration information particular to the computer (for any user).
HKEY_CLASSES_ROOT Is a subkey of HKEY_LOCAL_MACHINE\Software. The information stored here ensures that the correct program opens when you open a file by using Windows Explorer.
HKEY_CURRENT_CONFIG Contains information about the hardware profile used by the local computer at system startup.
The following table lists the data types currently defined and used by the system.
Data type Description
REG_BINARY Raw binary data. Most hardware component information is stored as binary data and is displayed in Registry Editor in hexadecimal format.
REG_DWORD Data represented by a number that is 4 bytes long. Many parameters for device drivers and services are this type and are displayed in Registry Editor in binary, hexadecimal, or decimal format.
REG_EXPAND_SZ A variable-length data string. This data type includes variables that are resolved when a program or service uses the data.
REG_MULTI_SZ A multiple string. Values that contain lists or multiple values in a form that people can read are usually this type. Entries are separated by spaces, commas, or other marks.
REG_SZ A fixed-length text string.
REG_FULL_RESOURCE_DESCRIPTOR A series of nested arrays designed to store a resource list for a hardware component or driver.

Caution
• Incorrectly editing the registry may severely damage your system. Before making changes to the registry, you should back up any valued data on your computer.
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Note
• To open Registry Editor, click Start, click Run, type , and then click OK.
• To safely use Registry Editor for such tasks as eliminating duplicate entries or deleting entries for programs that have been uninstalled or deleted, you should be prepared to both edit and restore the registry.