Predefined keys, which are defined by the system, help an application navigate in the Registry. You can also use them to develop tools that allow a system administrator to change whole categories of data. The following keys are defined at the root of the Registry:
These predefined keys are entry points to the Registry, and they are always open. This means that a developer does not have to call RegOpenKey first in order to work with the predefined keys. These keys are valid Registry handles for all Win32 implementations of the Registry, although use of the handles can vary from platform to platform.