Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

//Not supported on Windows 95 
//result = -1: scroll whole page 

function GetNumScrollLines: Integer;
 begin
   SystemParametersInfo(SPI_GETWHEELSCROLLLINES, 0, @Result, 0);
 end;

 procedure TForm1.Button1Click(Sender: TObject);
 begin
   ShowMessage(IntToStr(GetNumScrollLines));
 end;