Working with the Windows Home Server Registry : Starting the Registry Editor, Navigating the Registry

Starting the Registry Editor

As you see a bit later, the Registry’s files are binary files, so you can’t edit them directly. Instead, you use a program called the Registry Editor, which enables you to view, modify, add, and delete any Registry setting. It also has a search feature to help you find settings and export and import features that enable you to save settings to and from a text file.

To launch the Registry Editor, follow these steps:

Figure 1 shows the Registry Editor window that appears. (Your Registry Editor window might look different if someone else has used the program previously. Close all the open branches in the left pane to get the view shown in Figure 18.1.)

Figure 1. Running the REGEDIT command launches the Registry Editor, a program that enables you to view and edit the Registry’s data.

Navigating the Registry

The Registry Editor is reminiscent of Windows Explorer, and it works in basically the same way. The left side of the Registry Editor window is similar to Explorer’s Folders pane, except that rather than folders, you see keys. 

Navigating the Keys Pane

The Keys pane, like Explorer’s Folders pane, is organized in a treelike hierarchy. The five keys that are visible when you open the Registry Editor are special keys called handles (which is why their names all begin with HKEY). These keys are collectively referred to as the Registry’s root keys. I’ll tell you what to expect from each of these keys later. 

All these keys contain subkeys, which you can display by clicking the arrow to the left of each key or by highlighting a key and pressing the plus-sign key on your keyboard’s numeric keypad. To close a key, click the arrow, or highlight the key and press the minus-sign key on the numeric keypad. Again, this is just like navigating folders in Explorer.

You often have to drill down several levels to get to the key you want. For example, Figure 2 shows the Registry Editor after I’ve opened the HKEY_CURRENT_USER key, and then the Control Panel subkey, and then clicked the Keyboard subkey. Notice how the status bar tells you the exact path to the current key, and that this path is structured just like a folder path.

Figure 2. Open the Registry’s keys and subkeys to find the settings you want to work with.

Understanding the Registry Settings

If the left side of the Registry Editor window is analogous to Explorer’s Folders pane, the right side is analogous to Explorer’s Contents pane. In this case, the right side of the Registry Editor window displays the settings contained in each key (so I’ll call it the Settings pane). The Settings pane is divided into three columns:

Getting to Know the Registry’s Root Keys

The root keys are your Registry starting points, so you need to become familiar with what kinds of data each key holds. The next few sections summarize the contents of each key.

HKEY_CLASSES_ROOT

HKEY_CLASSES_ROOT—usually abbreviated as HKCR—contains data related to file extensions and their associated programs, the objects that exist in the Windows Home Server system, as well as applications and their Automation information. There are also keys related to shortcuts and other interface features.

The top part of this key contains subkeys for various file extensions. You see .bmp for BMP (Paint) files, .doc for DOC (Word or WordPad) files, and so on. In each of these subkeys, the Default setting tells you the name of the registered file type associated with the extension. For example, the .txt extension is associated with the txtfile file type.

These registered file types appear as subkeys later in the HKEY_CLASSES_ROOT branch, and the Registry keeps track of various settings for each registered file type. In particular, the shell subkey tells you the actions associated with this file type. For example, in the shell\open\command subkey, the Default setting shows the path for the executable file that opens. Figure 3 shows this subkey for the txtfile file type.

Figure 3. The registered file type subkeys specify various settings associated with each file type, including its defined actions.

HKEY_CLASSES_ROOT is actually a copy (or an alias, as these copied keys are called) of the following HKEY_LOCAL_MACHINE key:

HKEY_LOCAL_MACHINE\Software\Classes

The Registry creates an alias for HKEY_CLASSES_ROOT to make these keys easier for applications to access and to improve compatibility with legacy programs.

HKEY_CURRENT_USER

HKEY_CURRENT_USER—usually abbreviated as HKCU—contains data that applies to the user who’s currently logged on (which with Windows Home Server is almost always the Administrator account). It contains user-specific settings for Control Panel options, network connections, applications, and more.

Here’s a summary of the most important HKEY_CURRENT_USER subkeys:

HKEY_LOCAL_MACHINE

HKEY_LOCAL_MACHINE (HKLM) contains non–user-specific configuration data for your system’s hardware and applications. This is by far the most important key, and it’s where you’ll perform most of your Registry edits. You’ll use the following subkeys most often:

HKEY_USERS

HKEY_USERS (HKU) contains settings that are similar to those in HKEY_CURRENT_USER. HKEY_USERS is used to store the settings for users with group policies defined, as well as the default settings (in the .DEFAULT subkey) that are mapped to a new user’s profile.

HKEY_CURRENT_CONFIG

HKEY_CURRENT_CONFIG (HKCC) contains settings for the current hardware profile. If your machine uses only one hardware profile, HKEY_CURRENT_CONFIG is an alias for HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001. If your machine uses multiple hardware profiles, HKEY_CURRENT_CONFIG is an alias for HKEY_LOCAL_MACHINE\SYSTEM\ControlSetnnn, where nnn is the numeric identifier of the current hardware profile. This identifier is given by the Current setting in the following key:

HKLM\SYSTEM\CurrentControlSet\Control\IDConfigDB

Understanding Hives and Registry Files

The Registry database actually consists of a number of files that contain a subset of the Registry called a hive. A hive consists of one or more Registry keys, subkeys, and settings. Each hive is supported by several files that use the extensions listed in Table 1.

Table 2 shows the supporting files for each hive. (Note that all these files might not appear on your system.)

%SystemRoot%\System32\config\COMPONENTS
%SystemRoot%\System32\config\COMPONENTS.LOG
%SystemRoot%\System32\config\COMPONENTS.LOG1
%SystemRoot%\System32\config\COMPONENTS.LOG2

%SystemRoot%\System32\config\SAM
%SystemRoot%\System32\config\SAM.LOG
%SystemRoot%\System32\config\SAM.LOG1
%SystemRoot%\System32\config\SAM.LOG2

%SystemRoot%\System32\config\SECURITY
%SystemRoot%\System32\config\SECURITY.LOG
%SystemRoot%\System32\config\SECURITY.LOG1
%SystemRoot%\System32\config\SECURITY.LOG2

%SystemRoot%\System32\config\SOFTWARE
%SystemRoot%\System32\config\SOFTWARE.LOG
%SystemRoot%\System32\config\SOFTWARE.LOG1
%SystemRoot%\System32\config\SOFTWARE.LOG2

%SystemRoot%\System32\config\SYSTEM
%SystemRoot%\System32\config\SYSTEM.LOG
%SystemRoot%\System32\config\SYSTEM.LOG1
%SystemRoot%\System32\config\SYSTEM.LOG2

%SystemRoot%\System32\config\DEFAULT
%SystemRoot%\System32\config\DEFAULT.LOG
%SystemRoot%\System32\config\DEFAULT.LOG1
%SystemRoot%\System32\config\DEFAULT.LOG2

Also, the Administrator account has its own hive, which maps to HKEY_CURRENT_USER during logon. The supporting files for each user hive are stored in C:\Users\Administrator. The NTUSER.DAT file contains the hive data, and the NTUSER.DAT.LOG1 file tracks the hive changes.