Windows Registry 101

If you’re looking at this website, then there’s probably something wrong with your computer.  Perhaps you’ve narrowed it down to an issue with the Windows registry, and you’re wondering what the registry is and what it does, and how to repair it if it IS broken.

First things first – don’t attempt to open up the registry and tinker with it by hand.  It’s a very complex part of your computer and you could make things worse if you don’t know what you’re doing.  There are various programs that can help you clean the registry – we only suggest you use those if you want to do anything with the registry.

What Is The Windows Registry?

registryThe Windows registry is a flexible database used by the Windows operating system as well as the software installed in Windows to store and maintain personal settings, system configurations, user profiles, and other critical information.  It’s kind of a filing drawer where all the settings used by the operating system and your software are stored.  The registry is created by Windows and your software and drivers, and it can also be edited and changed by hand if necessary.

The Windows registry appeared with Windows 95, and it replaced the old INI file system.  The INI documents were small text based documents that were software specific.  However, the limitation was that they didn’t allow for multiple user settings.  Another problem was that they weren’t centrally located and if there was a problem it was harder to pin it down.

How Is The Windows Registry Organized?

The Windows registry is organized into a hierarchical structure, much like all the file systems on your computer.  Think of it as a tree-like structure.  For instance, when you save a picture you may save it in the My Documents \ My Pictures \ Photos file.  This is the same way that the registry is organized, and it is stored into a KEY \ SUBKEY \ VALUE structure.

There are six main root hives of the registry:

HKEY_CLASSES_ROOT
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
HKEY_CURRENT_CONFIG
HKEY_DYN_DATA

The registry is stored physically on your hard disk in the system.dat and user.dat files.  The system.dat stores values that have to do with your operating system and software, and the user.dat contains entries that pertain to the different user accounts on your system.

Fun Facts:  The infamous Millenium Edition (ME) version of windows had an additional classes.dat where HKEY_CLASSES_ROOT was stored.  Also, in computers on a network one might find a policy.pol file where network configurations are stored, typically created by the network administrator.

What Do The HKEYs Do?

The top most organizational structure of the registry are hives.  One hive might contain information pertaining to a user that is logged onto the computer, while another hive stores information related to general system settings.  Depending on the version of Windows that is running on your computer, there might be 5 or 6 hives.

Stored within the hives are keys, which can contain values (data) or further subkeys.  Think of keys as the “folders” of the registry.

Values are the actual data that the registry stores.  The data can be complied in various formats but the most common are binary, strings, and DWORD values.

An example registry key:

HKEY_CURRENT_USER \ Software \ Microsoft \ Internet Explorer \ Main \\ Start Page

In this case, HKEY_CURRENT_USER is the hive that all the data is stored in (in this case, it could be different for various users).  Software, Microsoft, Internet Explorer, and Main are all keys and subkeys.  The “Start Page” is the actual value where the information is stored, in this case the default web page that loads when you open Internet Explorer.

Cleaning The Registry

If you want to clean out the registry, we strongly suggest that you use a third party software tool to get the job done.  It’s much safer and faster than doing anything by hand.  We suggest RegCure Pro.  You can check out our RegCure Pro review here, or visit their main site here.

About the Author

Roger Feinstein has grown up with computers his entire life and strives to help others understand what goes on behind the scenes in their PCs. He's been writing tech articles for websites for over 5 years.

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