How badly?
If you only want the Switchboard to show, but don't mind the occasional
inquisitive user to get at the tables just by pressing F11 key, go to Tools,
Startu, and uncheck the Display Database Window.
If you don't want them to be able to use the F11 key, uncheck the Use Access
Special Keys box. WARNING: That might make it very difficult for you to ever
see the keys yourself!
You could also right click on each table and query and set them to Hidden.
Then go to Tools, Options, View tab and make sure that Hidden Objects and
System Objects are not checked. Still a bright user could know to check those
two options.
You could also rename every table and query with a USys in front of them. Of
course that would break all queries, forms, and reports. Plus checking the
System Objects box circumvents it.
If you really, really don't want users to see things like tables and
queries, you'll need to implement User Level Security and set permissions.
This is a MAJOR undertaking. Also it won't work with Access 2007 .acc
database files.