Workgroup (system database) specifying username and password using Microsoft.Jet.OLEDB.4.0
Connection string
This Microsoft Jet OLE DB 4.0 connection string can be used for connections to Access 97, Access 2000, Access 2002 and Access 2003.
Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\mydatabase.mdb;
Jet OLEDB:System Database=system.mdw;User ID=myUsername;Password=myPassword;