IOCTL_DISK_GET_DRIVE_LAYOUT_EX工作不正常

我有一个硬盘，上面有3个分区。当我使用IOCTL_disk_GET_DRIVE_LAYOUT_EX时，对象（在我的代码中是"pdg"对象）只返回数组1的分区信息，即使它说找到了4个分区。我缺少什么，使得partitionEntry（必须使用对象pdg的调试器进行partitionEntry）显示所有3个分区。我到处找了一些信息，但都找不到。不同的论坛，msdn。。。

下面是我的代码

#define UNICODE 1
#define _UNICODE 1
#include <windows.h>
#include <winioctl.h>
#include <stdio.h>
#define wszDrive L"\\.\PhysicalDrive3"
BOOL GetDrive(LPWSTR wszPath)
{
  HANDLE hDevice = INVALID_HANDLE_VALUE;  // handle to the drive to be examined 
  BOOL bResult   = FALSE;                 // results flag
  DWORD junk     = 0;                     // discard results
  DWORD hr;
  DWORD szNewLayout = sizeof(DRIVE_LAYOUT_INFORMATION_EX) + sizeof(PARTITION_INFORMATION_EX) * 4 * 25 ;
  DRIVE_LAYOUT_INFORMATION_EX *pdg = (DRIVE_LAYOUT_INFORMATION_EX*) new BYTE[szNewLayout];
  hDevice = CreateFileW(wszPath,          // drive to open
                        GENERIC_READ|GENERIC_WRITE,                // no access to the drive
                        FILE_SHARE_READ | // share mode
                        FILE_SHARE_WRITE, 
                        NULL,             // default security attributes
                        OPEN_EXISTING,    // disposition
                        0,                // file attributes
                        0);            // do not copy file attributes
  if (hDevice == INVALID_HANDLE_VALUE)    // cannot open the drive
  {
    hr = GetLastError();
      return (FALSE);
  }
  bResult = DeviceIoControl(hDevice,                       // device to be queried
                            IOCTL_DISK_GET_DRIVE_LAYOUT_EX, // operation to perform
                            NULL, 0,                       // no input buffer
                            pdg, szNewLayout,// sizeof(*pdg)*2,            // output buffer
                            &junk,                         // # bytes returned
                            (LPOVERLAPPED) NULL);          // synchronous I/O
  if(!bResult)
  {    
     hr = GetLastError();
     LPTSTR errorText = NULL;
     FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, hr, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPTSTR)&errorText, 0, NULL);
     wprintf(L"Error",   errorText);
  }
  CloseHandle(hDevice);
  return (bResult);
}

int wmain(int argc, wchar_t *argv[])
{
  BOOL bResult = FALSE;      // generic results flag
  bResult = GetDrive(wszDrive);
  system ("pause");
  return ((int)bResult);
}

感谢