编译VC程序是连接出错，请高手指点，谢谢！

这是错误提示：请高手指点一下，谢谢！
--------------------Configuration: WinMain - Win32 Debug--------------------
Compiling...
WinMain.cpp
Linking...
LIBCD.lib(crt0.obj) : error LNK2001: unresolved external symbol _main
Debug/WinMain.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.WinMain.exe - 2 error(s), 0 warning(s)-----------------------------------------------------------------------------------------
下面是原程序：
#include <windows.h>
#include <stdio.h>LRESULT CALLBACK WinSunProc(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
);int WINAPI WinMain(
  HINSTANCE hInstance,      // handle to current instance
  HINSTANCE hPrevInstance,  // handle to previous instance
  LPSTR lpCmdLine,          // command line
  int nCmdShow              // show state
)
{
WNDCLASS wndcls;
wndcls.cbClsExtra=0;
wndcls.cbWndExtra=0;
wndcls.hbrBackground=(HBRUSH)GetStockObject(BLACK_BRUSH);
wndcls.hCursor=LoadCursor(NULL,IDC_CROSS);
wndcls.hIcon=LoadIcon(NULL,IDI_ERROR);
wndcls.hInstance=hInstance;
wndcls.lpfnWndProc=WinSunProc;
wndcls.lpszClassName="Weixin2003";
wndcls.lpszMenuName=NULL;
wndcls.style=CS_HREDRAW | CS_VREDRAW;
RegisterClass(&wndcls); HWND hwnd;
hwnd=CreateWindow("Weixin2003","北京维新科学技术培训中心",WS_OVERLAPPEDWINDOW,
0,0,600,400,NULL,NULL,hInstance,NULL); ShowWindow(hwnd,SW_SHOWNORMAL);
UpdateWindow(hwnd); MSG msg;
while(GetMessage(&msg,NULL,0,0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return 0;
}LRESULT CALLBACK WinSunProc(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
)
{
//HDC hdc;
//PAINTSTRUCT ps;
switch(uMsg)
{
case WM_CHAR:
char szChar[20];
sprintf(szChar,"char is %d",wParam);
MessageBox(hwnd,szChar,"weixin",0);
break;
case WM_LBUTTONDOWN:
MessageBox(hwnd,"mouse clicked","weixin",0);
HDC hdc;
hdc=GetDC(hwnd);
TextOut(hdc,0,50,"计算机编程语言培训",strlen("计算机编程语言培训"));
ReleaseDC(hwnd,hdc);
break;
case WM_PAINT:
HDC hDC;
PAINTSTRUCT ps;
hDC=BeginPaint(hwnd,&ps);
TextOut(hDC,0,0,"维新培训",strlen("维新培训"));
EndPaint(hwnd,&ps);
break;
case WM_CLOSE:
if(IDYES==MessageBox(hwnd,"是否真的结束？","weixin",MB_YESNO))
{
DestroyWindow(hwnd);
}
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd,uMsg,wParam,lParam);
}
return 0;
}