What Every Windows User Needs to Know About the Windows Registry

In many respects, everything your Windows installation is can be found contained in the Windows Registry. Think of it like the master card index still available in most public libraries: all the contents of the library are stored on little cards in those file drawers.

In fact, in structure if not function, the Registry seems like a huge centralized database storing all the details of your Windows configuration, including the hardware, software, and customization applied to it.

Understand as you read that the Registry is an exhaustive topic in its own right, and no short section of a chapter can begin to do it justice because of the intricacies inherent in its design and detail.

Since its one of the core elements of Windows, and because it's not uncommon to be able to fix a problem with Windows, including many related to hardware issues (i.e., when an old device keeps being detected long after it's been removed because the Registry still contains an entry for it), your mastery of hardware troubleshooting increases in proportion to your knowledge of the Registry. Thus, we recommend you familiarize yourself with it along with safe editing techniques.

Let's look at some basics to understand about the Registry from your perspective:
- the core of the Registry is stored in two files - USER.DAT and SYSTEM.DAT - Windows 98 and later automatically backs up these files for you as the system starts, but you should always back them up yourself before editing the Registry
- the syntax of the Registry is exact; changes made to it must conform to the syntax or at best, the modification is ignored or at worst, Windows can fail on an unrecoverable Registry error, try to fix itself, and may or may not be able to do so
- much of the hardware, device drivers, and associated programs for your hardware are listed as entries, along with various services, options in the Windows printing subsystem, the Windows NT subsystem, and specific user preferences
- SCANREG is a utility included with many Windows versions to allow the scanning and repair of the Registry; to repair the Registry when you can, you work from the command line and type:

SCANREG /fix

- REGEDIT is the editor Windows includes to permit the viewing and editing of the Registry
- The Registry is organized into main or root keys that start with "Hkey_", then branches out to sub classifications (like CONFIG, ENUM, HARDWARE), and down to individual listings referred to as keys which may have both a subkey and value entries
- HKEY_LOCAL_MACHINE is the primary key to which machine-type information, including the details of your hardware configuration, is registered.
- HKEY_CURRENT_CONFIG looks to a section of HKEY_LOCAL_MACHINE called CONFIG to see what the hardware inventory is

Changes you make to your system, including the installation and removal of hardware and its drivers, should be reflected in the Registry, but sometimes fails to be registered or removed while the retention of out-of-date hardware entries can affect your ability to install new hardware or return resources for your use.

Familiarize yourself with the Registry, especially entries under the HKEY_LOCAL_MACHINE key, for a better understanding of your system as Windows sees it.