RegisterServer

procedure RegisterServer(const Is64Bit: Boolean; const Filename: String; const FailCriticalErrors: Boolean);

Registers the DLL/OCX with the specified filename. If Is64Bit is True, the DLL/OCX will be loaded as a 64-bit image and registered in a 64-bit process. If FailCriticalErrors is True, the system will not display any critical-error-handler message boxes. Raises an exception if not successful.

begin
  // Register hhctrl.ocx located in the System directory.
  RegisterServer(Is64BitInstallMode, ExpandConstant('{sys}\hhctrl.ocx'), False);
end;

Because we specify Is64BitInstallMode in the first parameter, it will register the 64-bit OCX in the 64-bit System directory when Setup is running in 64-bit mode. Otherwise, it will register the 32-bit OCX in the 32-bit System directory.