Two possible ways:
- Make more users (one for each windows user).
- Make the resource public (with public = Yes or guest ok = Yes) in /etc/samba/smb.conf

There's no sense in putting only a user...

Try install an ODBC driver for Linux
http://www.easysoft.com/developer/interfaces/odbc/linux.html

Then you can install an access connector and make a connection directly to the .mdb file through...