Before you change anything in the registry back it up.
You must at least make a backup of the key containing the data that you are going to change.
To do this select the key, and then select Registry from the toolbar.
Select Export Registry File, and when the save window opens select Selected Branch, then give your file a name and save it somewhere safe.
If all is not well after you make the change just import this file back into the registry.
Introduction to the Registry
The Windows Registry is a set of data files used to help Windows control hardware, software, the user's environment, and how Windows presents itself on screen.
The Registry information is contained in two files within the Windows directory, these are, SYSTEM.dat and USER.dat, there are also backup copies SYSTEM.da0 and USER.da0.
The Registry is accessed with regedit.exe which is in the Windows directory, or click on the START button, select RUN, type REGEDIT and press ENTER.
This central database is created by Windows during installation. The entries in this database consist of the hardware, software, users, and preferences data for a single PC, or any PC on a network. When the user makes changes to the Control Panel settings, File Associations, System Policies, or installed software, the changes are reflected in the Registry.
The Registry replaces the dreaded .INI files from Windows 3.1.
The Registry Editor displays the contents of the Registry in six subtrees called Keys.
Keys can contain data strings, as well as SubKeys.
Each of these six Keys begins with Hkey_ which indicates that it can be used by a program to access resources.
When you run the Registry Editor, it displays its' data in two panes. On the left side, you have the six Keys, which are shown as folders in "My Computer." Each key can have a set of values. Each value entry is comprised of three parts: the name of the key, its' data type, and the value itself.
The Registry Editor stores this information in .REG files, which are essentially text files containing the data in a specific format. If there is a small plus sign next to a key, then, it will have further data below called a SubKey. These are more commonly known as nested folders, which simply means that folders can themselves contain other folders.
The value entries in the right pane are associated with the selected key in the left pane. A value entry has three parts: the data type of the value (which appears as an icon), the name of the value, and the value itself. A value entry must limit itself to 64k or less, while the size of the actual total Registry is dependant on available hard disk space.
Data types can either be Binary numerical data or readable text. Most of the hardware information is stored as binary data, and can be displayed as either binary or hexadecimal information.
Right-click anywhere in the Registry Editor, and you can create a NEW Key (or subkey), string value, binary value, or DWORD value.
Hkey_Classes_Root
Is really a pointer to the HKEY_LOCAL_MACHINE\SOFTWARE\CLASSES, but it is often easier to edit the information from HKEY_CLASSES_ROOT than drilling down through the other handle keys.
In HKEY_CLASSES_ROOT you will find all the information necessary to launch application, including a mapping of which file types and extentions are associated with what programs and actions.
The Subkeys are arranged by pointer strings that are represented file types as listed in the options dialogue opened from any windows folder window.
Also present are Class ID numbers, which windows uses in place of names to uniquely identify and access data objects.DDE and OLE information and icons settings for various documents and programs are also in HKEY_CLASSES_ROOT.
It also contains software settings about drag-and-drop operations, handles shortcut information, and other user interface information. There is a subkey here for every file association that has been defined.
Hkey_Current_Config
This Key points to a branch of the Key Hkey_Local_Machine\Config that contains data about the current hardware configuration. If only one hardware exists the data here will be relatively constant.
Multiple hardware profiles (definable through control panel system applet) will place additional information in HKEY_LOCAL_MACHINE.
Under Windows 95 the user is prompted at the start-up to choose a hardware profile, Under WindowsNT the user selects a profile in the Last Known Good menu ( press spacebar at start-up). Whichever hardware configuration is selected, specific information is mapped into HKEY_CURRENT_CONFIG.
Hkey_Current_User
This Key points to a branch of Hkey_Users for the user who is currently logged onto the system.
Information here is essentially the same as that in HKEY_USERS with the exception that data for the default user is not included.
On a large network, settings here are used by the system to identify the proper configuration to access from HKEY_USERS
This key contains information regarding the currently logged-on user, see also HKEY_USERS
+ AppEvents: Settings for assigned sounds to play for system and applications sound events.
+ Control Panel: Control Panel settings, similar to system.ini, win.ini and control.ini in Windows 3.xx.
+ InstallLocationsMRU: Contains the paths for the Start-up folder programs.
+ Keyboard layout: Specifies current keyboard layout.
+ Network: Network connection information.
+ RemoteAccess: Current log-on location information, if using Dial-Up Networking
+ Software: Software configuration settings for the currently logged-on user.
HKEY_LOCAL_MACHINE:
Contains data about the hardware devices and software installed including how to make everything function. Hardware profiles, such as those defined for stand alone mode verses network connection and docked/undocked options for portable computers are here and differentiated by a unique ID which has its own Subkey.
This handle key also contains all security, network, and sharing information though that information cannot be edited directly in the HKEY_LOCAL_MACHINE, but has to be manipulated through Control Panel and NT’s User Manager for domains.
Like the rest of the Handle Keys, HKEY_LOCAL_MACHINE is overlapping, containing both HKEY_CLASSES_ROOT and HKEY_CURRENT_CONFIG.
Hkey_Users
Contains information relative only to the currently logged-in user, and the default user if different.
GUI options such as icons Star menu configuration, system colours, fonts, wallpaper, keyboard layout, etc are found here.
If administratively limited, which, if any, control panel applets are available to the current user is also contained within HKEYS_USERS.
Software developers know this Handle Key to be the place where they register their applications (in SOFTWARE subkey)
Hkey_Dyn_Data
This Key contains dynamic data that is gathered and written at start up and keeps track of Plug N’ Play devices and control hardware. Windows 95/98 only.
Plug N’ Play means that during a Windows session a new device may be installed and instantly usable.
Since the registry is only read at start up, HKEY_DYN_DATA required special handling to enable Plug N’ Play. As a result, HKEY_DYN_DATA is not written to the hard drive but resides in RAM.
At every start up, and when devices are added or removed, more than 1,600 potential configurations are calculated.
There is a way to force HKEY_DYN_DATA to write data to the hard drive, Choose the System Applet from Control Panel and select the Resource Tab, turn off Plug N’ play.
Hkey Handles, SubKeys
Hkey_Local_Machine may contain the following Subkeys:
SubKey
Config
Enum
Hardware
Network
Security
Software
System
|
Description
A collection of configurations for the local computer
Info. on the system's installed hardware devices
Info. on the ports and modems used with HyperTerminal
Info. Created when a user logs on to a networked PC
Info.on network security and remote administration
Info. about software and it's configuration on system
The database that controls system start-up, device driver loading, Windows 95 services, and OS behavior
|
Hkey_Local_Machine\Enum
Windows 95 bus enumerators are responsible for building the hardware tree. This includes assigning an identification code to each device on its bus and retrieving the device's configuration information, either directly from the device or from the Registry. For more information about the hardware tree and bus enumerators, see Introduction to System Configuration, and Windows 95 Architecture.
Bus enumeration information is stored in the Hkey_Local_Machine\Enum subtree. For all types of devices, subkeys contain information such as device type, assigned drive letter, hardware ID, and device manufacturer, plus driver-related information for network components.
The following table shows which devices are enumerated in typical subkeys.
Subkey
ESDI
FLOP
ISAPNP
Monitor
Network
Root
|
Device enumeration
Fixed disk devices
Floppy disk devices
Plug and Play devices on an ISA bus
Monitor devices
Network protocol, server, and bindings
Legacy devices
|
Hkey_Local_Machine\Config
The Hkey_Local_Machine\Config subtree contains information about alternate hardware configurations for the computer. For example, it can contain information about multiple configurations to be used when the computer is connected to a network, when it is undocked from a docking station, and so on. Each alternate configuration is assigned a unique identifier, and this configuration ID has a subkey under the Config key. Each configuration appears in the list of hardware profiles in the System option in Control Panel.
When Windows 95 checks the hardware configuration at system start-up, one of three things occurs:
In most situations, the configuration ID is mapped to a unique configuration and Windows 95 selects the appropriate one automatically, and the settings for the related Config subkey are used for system configuration.
If the user is starting the computer for the first time with new hardware components, Windows 95 creates a new configuration for the new configuration ID, and a new Config subkey is added to the Registry.
If the configuration ID is mapped to more than one configuration (for example, because Windows 95 cannot distinguish between two configurations), the user is prompted to choose which configuration to use.
Hkey_Local_Machine\Hardware
Information about serial ports and modems used with the HyperTerminal program
Hkey_Local_Machine\Network
Network information created when a user logs on to a networked computer, including the user name, primary network provider, whether the logon was validated by a server, and information about the system policies processor.
Hkey_Local_Machine\Security
Information about the network security provider and remote administration capabilities.
Hkey_Local_Machine\Software
The Hkey_Local_Machine\Software subtree contains configuration information about all installed software that can write information in the Registry. The entries in this key apply for anyone using this particular computer, and include definitions for file associations and OLE information. The software subkey contains, for example, the information you add when registering an application to use a specific filename extension and information added during installation of Windows-based applications.
The Hkey_Local_Machine\Software subtree contains several subkeys, including the Classes subkey, plus description subkeys for all installed software that can write to the Registry, as described in the following sections
Hkey_Local_Machine\System
The data in Hkey_Local_Machine\System is organised into control sets that contain a complete set of parameters for device drivers and services that can be loaded with Windows 95. All data that controls start-up is described in the CurrentControlSet subtree under Hkey_Local_Machine\System. This control set has two parts:
The Control key contains information used to control system start-up, including the computer's network name and the subsystems to start.
The Services key contains information to control the loading and configuration of drivers, file systems, and so on. The data in the Services key also controls how these services call each other.
