Understand How the Windows Registry Works - dummies

Understand How the Windows Registry Works

By Dan Gookin

The Registry contains information used by Windows and your programs. The Registry helps the operating system manage the computer, it helps programs use the computer’s resources, and it provides a location for keeping custom settings you make in both Windows and your programs.

For example, when you change the Windows desktop, the changes are stored in the Registry. When you see a list of recently opened files, that list is stored in the Registry. And, changes you make to the status bar in Word — yep, they’re kept in the Registry, too.

The Registry is essentially a database. Its information is stored on disk for the most part, though dynamic information also exists in the computer’s memory. (That dynamic information concerns the computer’s hardware and operating state.) All the information is organized by using a structure similar to folders in the file storage system.

The top level of the Registry contains hives, each of which starts with the curious word HKEY.

Registry Hives
Name Abbreviation Contents
HKEY_CLASSES_ROOT HKCR Information used by programs for file association and for sharing information.
HKEY_CURRENT_USER HKCU Settings and configuration for the current user.
HKEY_LOCAL_MACHINE HKLM Settings and configuration for all users.
HKEY_USERS HKU Settings and configuration for all users on the computer; the information in HKCU is copied from this hive when the user logs in.
HKEY_CURRENT_CONFIG N/A Hardware information about the PC’s resources and configuration.

Beneath the hives are folders, or keys. Keys can also have subkeys, just as folders have subfolders. The name of the game is organization.

Keys contain values. Every value has a name and data. Unlike the old ini files, the data can be something other than text, including numeric values and binary information. You can find several values in a single key, or a key can be empty or contain only subkeys.

As with files and folders, values stored in the Registry are found by following a pathname that gives the location of a specific key or value. For example, the following pathname to the key gives the location where Adobe Acrobat Reader 8.0 is installed on the computer:

HKCUSoftwareAdobeAcrobat Reader8.0InstallPath

The abbreviation HKCU for HKEY_CURRENT_USER is used in the preceding line. It’s followed by the subkeys Software, Adobe, Acrobat Reader, 8.0, and, finally, InstallPath. In the InstallPath key is a value that holds data in the form of text. The text is the pathname for the storage system location where Acrobat Reader 8.0 is installed.

Keys, like pathnames to files, can get long. Sometimes, a key name that’s too long to fit on a single line must be wrapped, such as


This key contains a binary value that determines whether Windows displays a shadow on the mouse pointer. The line is too long to fit on the page, so it wraps.

Incidentally, the CursorShadow key helps demonstrate a point that deserves emphasis: You can easily turn the mouse pointer shadow on or off by using the Pointers tab in the Mouse Properties dialog box. You don’t have to delve into the Registry, nor is there any benefit to doing so.

  • To view or modify the Registry, the Registry Editor program is used.

  • Some keys may be empty, though they still contain a Default value. That’s because all keys must contain a value or a subkey.