BOOL GetDiskFreeSpaceEx(
  LPCTSTR lpDirectoryName,  // pointer to the directory name
  PULARGE_INTEGER lpFreeBytesAvailableToCaller, // receives the number of bytes on
                                                // disk available to the caller
  PULARGE_INTEGER lpTotalNumberOfBytes,    // receives the number of bytes on disk
  PULARGE_INTEGER lpTotalNumberOfFreeBytes // receives the free bytes on disk
);