Another method is to establish a workgroup security file, and define the permissions of the users. This will cause a log-in to pop up when the db is opened, and depending on the log in, will allow different permissions to the admin, and also different users or groups of users.
This is a complicated and tricky procedure, but it's really well worth the effort. You must be careful that you don't lock yourself out of design mode, though - or even from opening the db at all!
The advantage over the mde file, is that the db can continue to be developed by the admin - the mde can't be opened in design mode by anyone and thus development is frozen. SO it's fine as long as you're finished developing the db, otherwise it's not the best method.
I can't detail all the steps involved, it's just too elaborate - there is a wizard though. Look under Tools-> Security -> User and Group permissions.
Maybe someone else can detail the procedure - but you're better off getting a good book on Access and reading the section on security.