var
 hWindow: HWND;
 msg: TMSG;
 WindowClass: TWndClassEx;
//...
function WindowCreate(WinCaption: PChar):HWND;
begin
 WindowClass.cbSize := sizeof (WindowClass);
 WindowClass.style := CS_HREDRAW or CS_VREDRAW;
 WindowClass.lpfnWndProc := @WindowProc;
 WindowClass.cbClsExtra := 0;
 WindowClass.cbWndExtra := 0;
 WindowClass.hInstance := HInstance;
 WindowClass.hIcon := LoadIcon (0,IDI_APPLICATION);
 WindowClass.hCursor := LoadCursor (0,IDC_ARROW);
 WindowClass.hbrBackground:=Color_BtnFace+2;
 WindowClass.lpszMenuName := nil;
 WindowClass.lpszClassName := CLASS_NAME;
 RegisterClassEx(WindowClass);

 Result:= CreateWindowEx(0,CLASS_NAME,WinCaption,
   WS_OVERLAPPED or WS_CAPTION or WS_SYSMENU or WS_THICKFRAME or
   WS_MINIMIZEBOX,100,100,WIN_WIDTH,WIN_HEIGHT,0,0,Hinstance,nil);

 SHOWWINDOW (hWindow,SW_Show);
end;
//...
hWindow := WindowCreate(WIN_CAPTION);

hWindow:= CreateWindowEx