uses 
  Registry; 

function GetIEVersion(Key: string): string; 
var 
  Reg: TRegistry; 
begin 
  Reg := TRegistry.Create; 
  try 
    Reg.RootKey := HKEY_LOCAL_MACHINE; 
    Reg.OpenKey('Software\Microsoft\Internet Explorer', False); 
    try 
      Result := Reg.ReadString(Key); 
    except 
      Result := ''; 
    end; 
    Reg.CloseKey; 
  finally 
    Reg.Free; 
  end; 
end; 


procedure TForm1.Button1Click(Sender: TObject); 
begin 
  ShowMessage('IE-Version: ' + GetIEVersion('Version')[1] + '.' 
    + GetIEVersion('Version')[3]); 
  ShowMessage('IE-Version: ' + GetIEVersion('Version')); 
  // <major version>.<minor version>.<build number>.<sub-build number> 
end;