12.6 Windows 9x/2000 Registry Problems
12.6.2 The Registry structure
Becoming familiar with the Registry structure subtrees and understanding the purpose of these subtrees will help to troubleshoot and maintain the computer. There is a key for every process that is running on the system. The following five subtrees or subtree keys are displayed in Registry Editor Window.

HKEY Notation
The Registry HKEY notation is as follows:

  • HKEY_USERS – Contains the system default settings data that is used to control individual user profiles and environments such as desktop settings, windows environment, and custom software settings.
  • HKEY_CURRENT_CONFIG – Contains data on the active hardware profile that is selected during the boot process. This information is used to configure settings for the device drivers to load and for the display resolution to use.
  • HKEY_CLASSES_ROOT – This subtree contains software configuration data of all the software that is installed on the computer.
  • HKEY_CURRENT_USER – Contains data about the current user logged onto the computer. Retrieves a copy of each user account that is used to log on to the computer and stores it in the registry.
  • HKEY_LOCAL_MACHINE – Contains all configuration data for the local computer, including hardware and operating system data such as bus type, system memory, device drivers, and startup control data. Applications, device drivers, and the operating system use this data to set the computer configuration. The data in this subtree remains constant, regardless of the user.
Figure is a exercise on registry keys.