function GetADOVersion: Double;
var 
  ADO: OLEVariant; 
begin 
  try 
    ADO    := CreateOLEObject('adodb.connection'); 
    Result := StrToFloat(ADO.Version); 
    ADO    := Null; 
  except 
    Result := 0.0; 
  end; 
end; 

// To use this function try something like: 
procedure TForm1.Button1Click(Sender: TObject); 
const 
  ADOVersionNeeded = 2.5; 
begin 
  if GetADOVersion then 
    ShowMessage('Need to install MDAC version 2.7') 
  else 
    ShowMessage(Format('ADO Version %n, is OK', [GetADOVersion])); 
end;