Access Database Limits
Access database (*.mdb or *.accdb) file size
2 gigabytes, including all objects in the database (data, forms, reports, indices, macros, modules, etc.)
Total number of concurrent users
255. Note that the practical limit will likely be lower than this based on database design.
Больше здесь: http://blogs.msdn.com/access/archive/2006/06/05/618366.aspx