[C++] How to get free disk space

int getFreeSpace(wstring wstrWorkingFolder)
{
 int nFreeSpace = 0;

 HINSTANCE hModule = ::LoadLibrary(L"KERNEL32.DLL");
 if(hModule)
 {
  PFNGETDISKFREESPACEEX pDiskFreeSpaceEx = NULL;

  // Determine function to use
  pDiskFreeSpaceEx = reinterpret_cast(::GetProcAddress(hModule, "GetDiskFreeSpaceExA"));
  if(!pDiskFreeSpaceEx)
  {
   DWORD dwSectorsPerCluster = 0;
   DWORD dwBytesPerSector    = 0; 
   DWORD dwFreeClusters      = 0; 
   DWORD dwClusters          = 0; 

   if(::GetDiskFreeSpace(wstrWorkingFolder.c_str(), &dwSectorsPerCluster, &dwBytesPerSector, &dwFreeClusters, &dwClusters) == TRUE)
   {
    nFreeSpace = dwFreeClusters * dwBytesPerSector * dwSectorsPerCluster;
   }
  }
  else
  {
   ULARGE_INTEGER uliFreeBytesAvailableToCaller;
   ULARGE_INTEGER uliTotalNumberOfBytes;
   ULARGE_INTEGER uliTotalNumberOfFreeBytes;

   if(::GetDiskFreeSpaceEx(wstrWorkingFolder.c_str(), &uliFreeBytesAvailableToCaller, &uliTotalNumberOfBytes, &uliTotalNumberOfFreeBytes) == TRUE) 
   {
    nFreeSpace = static_cast<__int64>(uliFreeBytesAvailableToCaller.QuadPart / (1024 * 1024));
   }
  }

  // Release library
  ::FreeLibrary(hModule);
 }
 return nFreeSpace;
}