RegOverridePredefKey function (winreg.h)

Maps a predefined registry key to the specified registry key.


LSTATUS RegOverridePredefKey(
  [in]           HKEY hKey,
  [in, optional] HKEY hNewHKey


[in] hKey

A handle to one of the following predefined keys:


[in, optional] hNewHKey

A handle to an open registry key. This handle is returned by the RegCreateKeyEx or RegOpenKeyEx function. It cannot be one of the predefined keys. The function maps hKey to refer to the hNewHKey key. This affects only the calling process.

If hNewHKey is NULL, the function restores the default mapping of the predefined key.

Return value

If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a nonzero error code defined in Winerror.h. You can use the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag to get a generic description of the error.


The RegOverridePredefKey function is intended for software installation programs. It allows them to remap a predefined key, load a DLL component that will be installed on the system, call an entry point in the DLL, and examine the changes to the registry that the component attempted to make. The installation program can then write those changes to the locations intended by the DLL, or make changes to the data before writing it.

For example, consider an installation program that installs an ActiveX control as part of an application installation. The installation program needs to call the control's DllRegisterServer entry point to enable the control to register itself. Before this call, the installation program can call RegOverridePredefKey to remap HKEY_CLASSES_ROOT to a temporary key such as HKEY_CURRENT_USER\TemporaryInstall\DllRegistration. It then calls DllRegisterServer, which causes the ActiveX control to write its registry entries to the temporary key. The installation program then calls RegOverridePredefKey again to restore the original mapping of HKEY_CLASSES_ROOT. The installation program can modify the keys written to the temporary key, if necessary, before copying them to the original HKEY_CLASSES_ROOT.

After the call to RegOverridePredefKey, you can safely call RegCloseKey to close the hNewHKey handle. The system maintains its own reference to hNewHKey.


Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header winreg.h (include Windows.h)
Library Advapi32.lib
DLL Advapi32.dll

See also


Registry Functions

Registry Overview