- A Windows registry is a centralized location in a computer running on a Windows operating system, which stores information on system settings, hardware configurations and user preferences. Any new hardware upgrade and installation information goes into the registry. It also stores any changes that a user makes to the settings, even desktop background or wallpaper. The Windows registry references these settings each time the user logs into the computer.
- The Windows Registry features hives, keys, sub-keys, and values. Hives are at the top of the hierarchy. It contains a certain category of information based on the configuration that applies to each user logged in and information on hardware installations. A Windows Registry may contain 5 to 6 different hives, depending on the operating system. Keys act as the organizational unit in the Windows Registry. They are the containers of values and additional sub-keys. Just like a folder that has a sub-folder, a key has a sub-key and may have further sub-keys of each sub-key. Each sub-key contains files of different values. Finally, the values contain the actual data in the file. Values can come in binary, strings and DWORD forms.
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Registry HivesThere are different hives that comprise a Windows Registry; they are HKEY_CURRENT_USER (HKCU), HKEY_LOCAL_MACHINE (HKLM), HKEY_CLASSES_ROOT (HKCR), HKEY_USERS (HKU), HKEY_CURRENT_CONFIG (HKCC) and HKEY_DYN_DATA (HKDD). Where H, stands for "Hive".
The HKEY_CURRENT_USER (HKCU) hive contains the preferences and configuration of a currently logged in user. When this user logs off and the next user logs in, the new user will get his own information, which is different from the other user, by using his particular information stored in this hive.
HKEY_LOCAL_MACHINE (HKLM) contains the configuration of the computer. This configuration does not change even when a different user logs in. This hive stays with the computer no matter who uses it.
HKEY_CLASSES_ROOT (HKCR) has the information pertaining to the file associations and shortcuts for each core user interface. Therefore, if user A logs in, he will only see his own files and not user B's files.
HKEY_USERS (HKU) keeps the information and credentials of all users who use the computer.
HKEY_CURRENT_CONFIG (HKCC) contains information of the configuration of the hardware. This hive links to the HKEY_LOCAL_MACHINE (HKLM) hive.
HKEY_DYN_DATA (HKDD) is for Windows 95/98/ME only. It contains the "Plug-and-Play" information of the hardware. This also links to the HKEY_LOCAL_MACHINE (HKLM) hive. -
Launching the Registry EditorIf you want to change the values contained in the Windows registry, you may use a program called registry editor. A computer running on Windows operating system already comes with the registry editor program, also known as regedit.exe for short. To launch the registry editor, you can click on "Start," then click on "Run." You want to then type in one word "regedit.exe" in the field, and then click on "OK" or press the "Enter" key on your keyboard. There are two panes in a registry editor. The left pane is for navigation which shows all the hives that expand by clicking on the "+" sign and contract by clicking on the "-" sign. Continue to expand the "+" key until you get to the specific sub-key. Once you click on the sub-key you are looking for, this will show on the right pane, which lists the values associated with the sub-key. You can make changes on the right pane to the Windows Registry. -
Perform a registry back up regularly.Take extreme care when working on Windows registry. It is important to run or save a back up of your registry before making any change. Should the change cause unexpected problems, then you can revert to the old registry. Modifying the Windows registry incorrectly can cause problems to the computer. Run anti-virus software that can scan the registry to find any virus attack. Some anti-virus software can create a regular back up of the registry, which you can go back to in case you need to reload the Windows registry.
