Ciao,
guarda io ho fatto in questo modo

// DataBase Name
$db = "C:\<my_dir>\<database>.mdb";

// Database Password
$passdb = "xxx";

// ADO Connection Creation
$sc = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source=$db;Persist Security Info=True;Jet OLEDBatabase Password=$passdb";

// ADO Object connection
$conn = new COM('ADODB.Connection') or exit('Cannot start ADO.');

// ADO Recordset
$rs = new COM("ADODB.Recordset");

// Open Connection
$conn->Open($sc);
Spero ti possa essere utile
ciao
Claudio