DeviceIoControl fails with opertion IOCTL_DISK_GET_DRIVE_LAYOUT

Hi I am trying to get the drive name(d:\,f:\) with DeviceIoControlfunction,
but it fails with error 5= Access is denied.
i am working with vista SP1,any way to to correct this error ?
if i will call the function with IOCTL_DISK_GET_DRIVE_GEOMETRY it will work
GREAT.
any reason why it fails if i used this operation:IOCTL_DISK_GET_DRIVE_LAYOUT
HERE IS THE CODE:

PARTITION_INFORMATION pdg;

hDevice = CreateFile(physicalDrive, // drive
        0, // no access to the drive
        FILE_SHARE_READ | // share mode
        FILE_SHARE_WRITE,
        NULL, // default security attributes
        OPEN_EXISTING, // disposition
        0, // file attributes
        NULL); // do not copy file attributes

if (hDevice == INVALID_HANDLE_VALUE) // cannot open the drive
 {
        return (FALSE);
}

bResult = DeviceIoControl(hDevice, // device to be queried
              IOCTL_DISK_GET_DRIVE_LAYOUT, // operation to perform
                                      NULL,
                                      0, // no input buffer
                                     &pdg,
              sizeof(pdg), // output buffer
                                     &junk, // # bytes
returned
                                     (LPOVERLAPPED) NULL); // synchronous I/O

if(! bResult)
{

      win = GetLastError();
}