Как использовать CreateWindow(Ex)?

program winmin;

uses
 windows,
 messages;
var   wc : TWndClassEx;
MainWnd : HW   Mesg : TMsg;   

function WindowProc(wnd:HWND; Msg : Integer; Wparam:Wparam;
 Lparam:Lparam):Lresult; stdcall;
Begin
 case msg of
 wm_destroy :
  Begin
   postquitmessage(0); exit;
   Result:=0;
  End;

  else Result:=DefWindowProc(wnd,msg,wparam,lparam);
 end;

End;

var xPos,yPos,nWidth,nHeight : Integer;
begin
 wc.cbSize:=sizeof(wc);
 wc.style:=cs_hredraw or cs_vredraw;
 wc.lpfnWndProc:=@WindowProc;
 wc.cbClsExtra:=0;
 wc.cbWndExtra:=0;
 wc.hInstance:=HInstance;
 wc.hIcon:=LoadIcon(0,idi_application);
 wc.hCursor:=LoadCursor(0,idc_arrow);
 wc.hbrBackground:=COLOR_BTNFACE+1;
 wc.lpszMenuName:=nil;
 wc.lpszClassName:='WinMin : Main';

 RegisterClassEx(wc);
 xPos:=100;
 yPos:=150;
 nWidth:=400;
 nHeight:=250;

 MainWnd:=CreateWindowEx(
   0,              
   'WinMin : Main',
   'Win Min',        
   ws_overlappedwindow,
   xPos, 
   yPos,
   nWidth,   
   nHeight,        
   0,               
   0,                  
   Hinstance,          
   nil                 
 );


 ShowWindow(Mai! nWnd,CmdShow);
 While GetMessage(Mesg,0,0,0) do
 begin
  TranslateMessage(Mesg);
  DispatchMessage(Mesg);
 end;

end.