Windows Server 2003 Resource Kit Registry Reference

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Welcome to the Resource Kit Registry Reference for Windows Server 2003.

The Registry Reference is a searchable technical reference that provides detailed descriptions of selected Windows Server 2003 registry content. It describes the subtrees, keys, subkeys, and entries that advanced users want to know about, including many entries that cannot be changed by using Windows tools or programming interfaces. It also contains essential background information about the Windows registry, as well as methods of backing up and restoring the registry, and tips on how to edit the registry safely.

Caution

• Directly editing the registry bypasses standard safeguards, allowing settings that can damage your system, or even require you to reinstall Windows. If you are certain that you must edit the registry, first back it up by using one of the methods described in Backing Up and Restoring the Registry. After you make changes, be sure to test them before returning your computer to normal operation.

For more information, see one of the following:

• HKEY_CURRENT_CONFIG
• HKEY_CLASSES_ROOT
• HKEY_CURRENT_USER
• HKEY_LOCAL_MACHINE
• SYSTEM
• About the Registry Reference

HKEY_CURRENT_CONFIG (HKCC)

Description

The HKEY_CURRENT_CONFIG (HKCC) subtree stores configuration data for the current hardware profile.

This subtree does not contain any data. It just stores a pointer to the content of the

Hardware ProfilesCurrent subkey in the

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetCurrentControlSetHardware Profiles subkey.

The content of the Current subkey appears in HKEY_CURRENT_CONFIG, and it can be viewed and changed in either location. This subtree provides easier access to the data.

 

HKEY_CLASSES_ROOT (HKCR)

Description

The HKEY_CLASSES_ROOT subtree contains two types of data:

1. Data that associates file types with programs. The file type subkeys in HKEY_CLASSES_ROOT have the same name as the file name extension for the file type, such as .exe. File type associations are stored in the registry, but you should use Windows Explorer to change them. In Windows Explorer, from the Tools menu, click Folder Options, and then click the File Types tab.
2. Configuration data for COM objects, Visual Basic programs, or other automation. The configuration subkeys use either the program IDs (such as for COM, Visual Basic, automation, and scripting) or parent keys for other classes of information (such as for CLSID, Interface, TypeLib, AppId, and so on).

The content of HKEY_CLASSES_ROOT comes from two sources: HKEY_LOCAL_MACHINESOFTWAREClasses and HKEY_CURRENT_USERSOFTWAREClasses. If a subkey or entry appears in either location, then it also appears in HKEY_CLASSES_ROOT. If the values of entries in the two Classes subkeys conflict, then only the value in HKEY_CURRENT_USERSOFTWAREClasses appears in HKEY_CLASSES_ROOT.

In Windows NT 4.0 and earlier, HKEY_CLASSES_ROOT displayed the data only in HKEY_LOCAL_MACHINESOFTWAREClasses. The current, merged configuration lets the system independently register program classes for each user. This feature is known as per-user class registration.

Per-user class registration has several benefits:

• Multiple users can customize a single computer. For example, one user can install an application that uses a particular file type, and another user can install a different application that uses the same file type without affecting the first user.
• Roaming class registration. Because class registrations are stored in the user profile, the class registrations are loaded on each computer through the application management extension after the profile is loaded. When the user logs on to a different computer, the registration travels with the user through the directory and is written to a local portion of the user profile.
  Note: Roaming class registration is only available when using Intellimirror Software Management.
• Increased registry security. Previously, users could change or delete registry keys in HKLMSOFTWAREClasses, thus breaking an application or changing its behavior. However, with class information now written to the user profile, a system administrator can limit access to HKLMSOFTWAREClasses.

 

HKEY_CURRENT_USER (HKCU)

Description

The HKEY_CURRENT_USER subtree contains the user profile for the user who is currently logged on to the computer. The user profile includes environment variables, personal program groups, desktop settings, network connections, printers, and application preferences. The data in the user profile is similar to the data stored in the Win.ini file in Windows 3.x.

The HKEY_CURRENT_USER subtree does not contain any data. It just stores a pointer to the content of the HKEY_USERSSecurity ID (SID) of current user subkey. Therefore, the content of that subkey also appears in HKEY_CURRENT_USER, and it can be viewed and changed in either location. The HKEY_CURRENT_USER subtree just provides easier access to the data.

A new HKEY_CURRENT_USER subtree is created each time a user logs on. The data for the subtree comes from the profile of the current user. If no profile is available, then the subtree is built from the user profile settings established for a default user, which are stored in System driveDocuments and SettingsDefault User (WINNT)Ntuser.dat.

 

HKEY_LOCAL_MACHINE (HKLM)

Description

The HKEY_LOCAL_MACHINE subtree contains information about the local computer system, including hardware and operating system data, such as bus type, system memory, device drivers, and startup control parameters.

 

SYSTEM (HKLMSYSTEM)

Description

The subkeys in the HKEY_LOCAL_MACHINESYSTEM key store entries for the current control set and for other control sets that can be used, or have been used, to run Windows Server 2003. Windows Server 2003 maintains at least two control sets to ensure that the system always starts.

 

Reference: http://technet.microsoft.com/en-us/library/cc778196(WS.10).aspx