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Windows Showcases and Review >> The Windows Core: Understand the Registry Database

Almost each and every systemtuning tweak that you find on this page requires changes in the Windows Registry. It is a vast database that Windows uses to save settings, configurations and other facts like software or hardware information. The registry is constructed hierarchically and pretty similar to the known Windows file system: Weve got keys (folders) and values (files) and even data types (file extensions). The Registry consists out of 5 main keys which all start with the letter H that stands for Hive thus referring to the hierarchic structure of the registry...
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The Windows Registrys 5 main keys

Key name

Description

HKEY_CLASSES_ROOT

A direct link to HKEY_LOCAL_MACHINE\SOFTWARE\Classes as well as HKEY_USERS/User SID (like S-1-5-17). Here you can find a long list of file extensions and installed applications. It defines which action is performed with each file extension.

HKEY_CURRENT_USER

All configurations, settings, information and actually a lot more data for the currently logged-in user is available here. This main key uses the global settings from HKEY_USERS.

HKEY_LOCAL_MACHINE

This key includes settings and information for your specific machine: These have a higher priority than the ones from HKEY_CURRENT_USER and apply for all system users. HKLM contains the important subkeys SYSTEM, SAM, SECURITY, SOFTWARE and HARDWARE.

HKEY_USERS

Here you will find global settings for each unique user. They are the basis for HKEY_CURRENT_USER. The user identifications takes place through the SID (Security Identifier) instead of the actual user name.

HKEY_CURRENT_CONFIG

Connected with HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Hardware Profiles\Current. Displays all the information regarding the hardware of your computer.

HKEY_PERFORMANCE_DATA (not visible on every machine)

Allows applications to access performance data. This key will be created when needed by applications and is not visible in a standard installation.

Note: The five important keys from HKEY_LOCAL_MACHINE can be found at %Windows%\system32\config. HKEY_USERS\UserProfil is located under C:\Documents and Settings\User name and C:\Documents and Settings\Sandro Villinger\Local Settings\Application Data\Microsoft\Windows.

            

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Understanding the different data types
The actual information in the Windows Registry lies in the thousands of values which have different data types:

Datentyp

Erklärung

String value (REG_SZ)

A text string.

Binary value (REG_BINARY)

Consists out of the values 0 and 1. Usually found in hardware configuration settings.

DWORD value (REG_DWORD)

Specifies the state of a function/setting (0 for disabled, 1 for enabled).

Multi-string value(REG_MULTI_SZ)

A group of text strings that are separated by a zero byte.

Expandable String value (REG_EXPAND_SZ)

A text string with an environemtal variable (e.g. %WINDOWS% stands for the Windows directory; no matter where it is located).
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Additional information and how to use the Registry accordingly
The Registry can be viewed and edited by a special program like the Registry Editor (comes with Windows). To open up this editor, you need to click on Start/Run and enter regedit. Hit OK to start the application.

   

At first sight you will immediately recognize the structure of the Windows Explorer. Although, like we told you, folders are named Keys and files are Values. A click on the + or a double-click of HKEY_LOCAL_MACHINE (for example) expands this main key.
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How to backup the Windows Registry
If you feel uncertain about changing the Registry, which is a key component of Windows, you might want to play safe and create a backup. And its as simple as this:

1. Open up the Registry Editor and go to the specific key (e.g. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control as seen above). Right-click on the subkey Control and select Export.

                  

2. A window appears that asks you to save this subkey as a .reg-file. Enter a name (like Control_Backup.reg and hit Save. In case of an emergency just double-click on the .reg-file and click OK/OK to integrate your old settings into the Registry!
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