First, make sure you are using the split front-end and back-end file method. This is where you have one database file that has nothing the the tables in it. This file is called the Back-end file. You then have another file that has all of your forms, queries, reports and modules in it. The tables in the back-end file are linked to the front-end file.
Using either version of Access, the simple way to protect your application from users is to make a compiled type file and let them use that version. This is referred to as creating an mde (accde in Access 2007)file. There is an option on the menu to perform this conversion. Just make sure you have a backup copy of your front-end file before you do this.
You will not be able to make change to the mde (accde in Access 2007), therefore, you would continue to make updates a fixes in your mdb file.