Chapter 5 :Registry : what and how

Chapter 5 : Registry : what and how

The Registry has to be one of the least understood aspects of the Windows operating system family. Even seasoned professionals approach it with a degree of caution, knowing that a wrong entry can potentially wreak havoc on the system. To understand the Registry is to get to the heart of controlling and modifying your Widows system. With a detailed understanding of what you are doing, you can turn your machine into a lean performance machine, customize and personalize its appearance, and get fine-grained control over nearly every aspect of how Widows XP behaves.

Some History

The Registry was introduced as a way out of the "INI files mess" that plagued early versions of Windows. Configuration information regarding the operating system, application files, hardware, and so on were stored in INI files scattered all over the system. For example, when an application is installed, it needs to know various parame­ters regarding the operating system and the available hardware. Much of this information is common to other applications as well. However, if there was any change in the hardware or operating sys­tem software, updating the application's INI files used to be hell.

The Registry was conceived as a way out of this madness. It is a hierarchical database that stores information regarding the hard­ware, operating system software, application software, users prefer­ences and system preferences. The hierarchy separates the machine information, user information and the software information into logically discrete units that can be manipulated with greater ease. Any changes made by users, the operating system, newly installed software, and hardware are all updated and reflected in the Registry.

During system startup, Windows uses the registry to get con­figuration data regarding the hardware, software and other peripherals that have been configured. It also maintains a backup copy of the registry with which the system had successfully start­ed up last. Hence, if it encounters a problem with the current startup, it can then use the configuration information from the backup to attempt to start the system. Some of the information stored in the registry is specific to the particular startup session only, and is mostly user-specific. When a user installs new soft­ware, Windows will either make the installation user-specific .or system-wide. In some software, the user is given the option to select whether the installation should or not be available to every­one else who uses the system. In other cases, the software will install itself system-wide and save user specific information sepa­rately, making entries in the registry that are both user-specific as well as system-wide.

For example, when you install Microsoft Office, the program is installed system-wide, but the user information is specific to the cur­rently logged-in user. Any preferences that are made are stored under the username in the registry. If another user logs in and starts Microsoft Office, the default preferences are initialised, and a new entry is created in the Registry under this username.

This flexibility has deeper significance when considering a net­worked scenario. Administrators can specify user rights and access to various system and network components. They can control what users can and cannot do on their machines with a fair degree of granular control. For example, Administrators can specify that users are not allowed to install new applications on their machines. A Registry entry disabling the users' right to install would secure the system. And a Registry entry can be made to prevent unauthorized access to the registry itself

However, the Registry has not done away entirely with the legacy of INI files, partially due to Microsoft's commitment to backward compatibility and partially because in some cases the Registry wouldn't be available-as in the case of the boot process, when the boot.ini file is used to get the initial startup information.

Critics of the Registry concept point to it ~ a "single point of fail­ure." If the Registry is damaged, XP will fail to start up, and in most cases will require a complete reinstall. It is for this reason that the Registry is hidden deep in the system, and any discussion on the tweaking the Registry is accompanied by dire warnings of disaster if one does anything wrong. Also, if an application doesn't uninstall correctly, it can leave traces in the registry, which over time will increase its size and affect performance.

Physically, the Registry information in' XP is stored in multiple files in the \System32\Config folder of the operating system (or root) folder-usually C:\ Windows or C:\ WINNT. These files cannot be edit­ed directly; they have to be accessed through a Registry-editing pro­gram such as Regedit.exe or Regedt32.exe.

Through the registry many problems / irritation can be resolved. as this is not for the learners and beginner. Any incorrect change in registry will bring crash of the operating system; the same is not published here. Any one who is well versed with computer may contact me at the mail address given above.