Introduction

Have you ever encountered a situation when urgent work had to be done, but strange and frightening messages appeared on screen, informing you that the operating system couldn't be loaded because of registry corruption? For example, among Windows NT 4.0 users, there are many persons who were shocked by the following message during the system boot:

     OS Loader V 4.0     ....     Windows NT could not start because the following file is missing or     corrupt:     \WINNT\SYSTEM32\CONFIG\SYSTEM     You can attempt to repair this file by Starting Windows NT Setup using     the original Setup floppy disk or CD-ROM.     Select 'r' at the first screen to repair. 

If you've already migrated to Windows 2000 or Windows XP, you might see almost the same message:

     Windows 2000/XP could not start because the following file is missing     of corrupt:     \WINNT\SYSTEM32\CONFIG\SYSTEM     You can attempt to repair this file by starting Windows 2000/Whistler     Setup using the original Setup floppy disk of CD-ROM.     Select 'r' at the first screen to repair. 

The examples provided above clearly show that a single error in the system registry (the System file mentioned in the messages shown above contains registry information) can influence the whole system configuration and even prevent the operating system from booting. Furthermore, there are some applications, which can run correctly only after editing the system registry. For this reason, the importance of understanding the registry and having practical skills to be able to work with it can't be underestimated.

The registry is difficult to decipher and understand. However, it's one of the most important components of any modern operating system belonging to the Windows family. Neither Windows 9x/ME nor Windows NT/2000/XP can run without it. So, what exactly is the registry? It's a centralized database that stores all the settings of the operating system and the applications running in it. This makes the registry similar to various INI files, and also to files like Autoexec.bat and Config.sys used in earlier Windows versions. The registry also stores information on all the hardware, including Plug and Play devices, OLE data, and file associations. The registry contains all the data concerning the applications that support Plug and Play and OLE, networking parameters, hardware profiles, and user profiles.

To summarize, if there's any hardware or software in the computer system that influences it in some way, you can be sure that the system registry stores information on that component.