C语言编写的DOS程序，怎样转换为windows窗口程序？

#include
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT ("HelloWin") ;
HWND hwnd ; //窗口句柄
MSG msg ; //消息结构
WNDCLASS wndclass ; //窗口类结构
wndclass.style = CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc = WndProc ;
wndclass.cbClsExtra = 0 ;
wndclass.cbWndExtra = 0 ;
wndclass.hInstance = hInstance ;
wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;
wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;
wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
wndclass.lpszMenuName = NULL ;
wndclass.lpszClassName = szAppName ;

//如果注册窗口失败，弹出错误对话框
if (!RegisterClass (&wndclass))
{
//在Windows 98中，大多数Unicode函数无法执行，MessageBoxW是个例外
MessageBox (NULL, TEXT ("This program requires Windows NT!"),
szAppName, MB_ICONERROR) ;
return 0 ;
}

//建立窗口
hwnd = CreateWindow (szAppName, // window class name
TEXT ("The Hello Program"), // window caption
WS_OVERLAPPEDWINDOW, // window style
CW_USEDEFAULT, // initial x position
CW_USEDEFAULT, // initial y position
CW_USEDEFAULT, // initial x size
CW_USEDEFAULT, // initial y size
NULL, // parent window handle
NULL, // window menu handle
hInstance, // program instance handle
NULL) ; // creation parameters

ShowWindow (hwnd, iCmdShow) ; //显示窗口
UpdateWindow (hwnd) ; //重画显示区域
//消息循环，用于从消息队列中取出消息，并做相应处理
while (GetMessage (&msg, NULL, 0, 0))
{
TranslateMessage (&msg) ;
DispatchMessage (&msg) ;
}
return msg.wParam ;
}

//窗口消息处理程序
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
HDC hdc ;
PAINTSTRUCT ps ;
RECT rect ;

switch (message)
{
case WM_CREATE:
PlaySound (TEXT ("hellowin.wav"), NULL, SND_FILENAME | SND_ASYNC) ;
return 0 ;

case WM_PAINT:
hdc = BeginPaint (hwnd, &ps) ;
//GetClientRect函数检索一个窗口的客户区坐标rect
GetClientRect (hwnd, &rect) ;
char buf[80];

sprintf(buf,"char 数据类型长度：%d\nstring 数据类型长度：%d\n",sizeof((char)'a'),sizeof("a"));
DrawText (hdc, TEXT (buf), -1, &rect,
DT_SINGLELINE | DT_CENTER | DT_VCENTER) ;
EndPaint (hwnd, &ps) ;
return 0 ;

case WM_DESTROY:
PostQuitMessage (0) ;
return 0 ;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}