The Microsoft Access database option is primarily intended for evaluation purposes or for very small bulletin boards. Microsoft Access is a desktop application and is not intended for multi-user server environments. Nevertheless it offers a quick setup with almost no effort.
The file TemplateDatabase.mdb is located in your installation archive. This file contains a blank BBS database in Microsoft Access 2000 format (the 2000 format can be loaded into Access 2003 and Access 2007 without conversion problems). You do not need to do anything with this file in order to run the evaluation BBS. However, make a note of it because you will need it when creating a completely new BBS.
It is possible to downscale from SQL Server to Microsoft Access. This may be desired for testing (e.g. you want to create a test system without the overhead of running a new SQL Server database). It is also a convenient way of packaging the BBS data into a format that can be distributed to people without SQL Server.
All table structures and field types are compatible and therefore no issues should occur during the data transfer.