Remote folders etc should automatically use the creditials of the logged-in user.
For mdbs... Access help says this:
In order for the Enable system administrator (SA) user name check box to be enabled, the following must be true.
The Access project must be connected to a SQL Server 7.0 (or later) database or a Microsoft SQL Server 2000 Desktop Engine.
The SQL Server database must be running on a Windows Server platform.
The SQL Server must be running on the same computer as the Access project.
The current Windows user must be an Administrator for the computer.
The current SQL Server user must be a member of the System Administrator role.