Inno wizard window size seem to change between Win7 and XP causing bitmap issue

Question

Inno wizard size seem to change between Win7 and XP

I have a bitmap loaded on screen, but it does not fit to XP? Also I am trying to paint to specific place on picture (x,y) but the position changes between XP and Win7. I am using ScaleX() and Scaley()

what options do I have? how to force scaling bitmap properly or how to detect window size?

    function install_CreatePage(PreviousPageId: Integer): Integer;
  var
    Page: TWizardPage;
  begin
    Page := CreateCustomPage(
      PreviousPageId,
      ExpandConstant('{cm:e_installCaption}'),
      ExpandConstant('{cm:e_installDescription}')
    );


  //   BitmapImage1
    BitmapImage1 := TBitmapImage.Create(Page);
 try 
 begin
    with BitmapImage1 do
    begin
      Parent := Page.Surface;
      Left := ScaleX(1);
      Top := ScaleY(1);
      Width := ScaleX(497);
      Height := ScaleY(244);
       ExtractTemporaryFile('g_screen.bmp') ;
       Bitmap.LoadFromFile(ExpandConstant('{tmp}')+'\g_screen.bmp') ;
    end
    end
 except
    BitmapImage1.height := 0;
    end;

{ Label3 }
BingLabel1 := TLabel.Create(Page);
with BingLabel1 do
begin
  Parent := Page.Surface;
  Left := ScaleX(37);
  Top := ScaleY(159);
  Width := 174;// ScaleX(174);
  Height := ScaleY(16);
  Caption := 'this text does not go right in all machines !';
  Font.Name := 'Tahoma';
end;

Answer 1

Can you post your script?
How big is the bitmap?
Is Win7 or WinxP showing the correct behavior?