Registry Root Keys

Everyone who has been working on a computer might have faced some types of problems. Under such situations, you might have googled to find a solution to your problem. Finally, you find out a solution in one of the microsoft support page. To the best part of it, the support page advices you to modify certain registry values. Nevertheless, the support page also puts a warning message identical to the one below.

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall Operating System. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

Now, you are in a real dilemma… Should I or shouldn’t I……. In this post, I intend to give the readers a brief idea about the Registry Root Keys.

If you open the Registry Editor (Start –> Run –> regedit), you can see the following five Registry root Keys.


Let me tell you about these five classes now.

This can be considered as a pointer or reference to HKEY_LOCAL_MACHINE\Software\Classes. If it is a reference, then why do we need such a root key itself? A genuine question for a normal man. This class is generally used by the developers, since they are mainly filled with information with regard to the applications, file associations etc.

Also referred to as HKCR

This node contains information related to a user account that exists in the computer. Information regarding the mapped network drives, etc are stored in this hive.

Also referred to as HKCU

This node contains information of the computer. You should understand that the registry settings under this hive is applicable to all the users logging in to the computer. Hence, any settings configured under this node will be applied to all the users logging in to the computer. Eg. If USB is disabled in HKEY_LOCAL_MACHINE, it will remain disabled for all the users logging in to the machine.

Also referred to asHKLM

This hive contains settings retrieved from the group policy object. Group Policy is one central tool, which a Server Engineer will use to define certain specific settings to a group of users/computers. The settings applied to the users will be contained in this registry hive. When a user login to the computer, these settings are copied to HKCU registry hive. If you expand this registry hive, a folder called DEFAULT can be seen. This folder contains all the settings which are global to all the users. Other than the DEFAULT folder, you can also see many other folders, whose names are actually the SID’s of different users. (In Windows machine, each logon account has a unique SID). Each of these SID folders contain the settings which are unique to each of the users.

Also referred to as HKU

This registry hive contains all the profile settings under which the computer is turned on now. This is also a pointer or reference to HKLM\System\CurrentControlSet001.

Also reffered to as HKCC

Hope this has been of some help to you. I would be happy to believe that I was able to spread atleast a little bit of knowledge to everyone who read this article. All  your comments are welcome.


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