初学directdraw 求解啊解决办法

初学directdraw 求解啊
我刚学的directdraw 
下面这段代码就是一个hello world 代码 然后我声明了个lpdirectdraw7 lpDD 
不知道为什么老是有问题啊
求解啊

#include "stdafx.h"
#include "resource.h"
#include <ddraw.h>
#include <windows.h>
#pragma comment(lib,"ddraw.lib")
#pragma comment(lib,"dxguid.lib")


#define MAX_LOADSTRING 100

LPDIRECTDRAW7 lpDD;
// Global Variables:
HINSTANCE hInst; // current instance
TCHAR szTitle[MAX_LOADSTRING]; // The title bar text
TCHAR szWindowClass[MAX_LOADSTRING]; // The title bar text

// Foward declarations of functions included in this code module:
ATOM MyRegisterClass(HINSTANCE hInstance);
BOOL InitInstance(HINSTANCE, int);
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK About(HWND, UINT, WPARAM, LPARAM);

int APIENTRY WinMain(HINSTANCE hInstance,
  HINSTANCE hPrevInstance,
  LPSTR lpCmdLine,
  int nCmdShow)
{

  // TODO: Place code here.
MSG msg;
HACCEL hAccelTable;

// Initialize global strings
LoadString(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
LoadString(hInstance, IDC_DIRECTX2, szWindowClass, MAX_LOADSTRING);
MyRegisterClass(hInstance);

// Perform application initialization:
if (!InitInstance (hInstance, nCmdShow)) 
{
return FALSE;
}

hAccelTable = LoadAccelerators(hInstance, (LPCTSTR)IDC_DIRECTX2);

// Main message loop:
while (GetMessage(&msg, NULL, 0, 0)) 
{
if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg)) 
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}

return msg.wParam;
}



//
// FUNCTION: MyRegisterClass()
//
// PURPOSE: Registers the window class.
//
// COMMENTS:
//
// This function and its usage is only necessary if you want this code
// to be compatible with Win32 systems prior to the 'RegisterClassEx'
// function that was added to Windows 95. It is important to call this function
// so that the application will get 'well formed' small icons associated
// with it.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
WNDCLASSEX wcex;

wcex.cbSize = sizeof(WNDCLASSEX); 

wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = (WNDPROC)WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = LoadIcon(hInstance, (LPCTSTR)IDI_DIRECTX2);
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName = (LPCSTR)IDC_DIRECTX2;
wcex.lpszClassName = szWindowClass;
wcex.hIconSm = LoadIcon(wcex.hInstance, (LPCTSTR)IDI_SMALL);

return RegisterClassEx(&wcex);
}

//
// FUNCTION: InitInstance(HANDLE, int)
//
// PURPOSE: Saves instance handle and creates main window
//
// COMMENTS:
//
// In this function, we save the instance handle in a global variable and
// create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
  HWND hWnd;

  hInst = hInstance; // Store instance handle in our global variable

  hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
  CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);

  if (!hWnd)
  {
  return FALSE;
  }

  ShowWindow(hWnd, nCmdShow);
  UpdateWindow(hWnd);

  return TRUE;
}

//
// FUNCTION: WndProc(HWND, unsigned, WORD, LONG)