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.