With different versions of MDAC available it is sometimes
useful to know that your application won’t fail because a user
hasn’t got the latest version installed.
The following function returns the ADO version installed,
you need to place ComObj in the uses clause to use this function.

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;