As previously stated, converting your MDB frontend to an MDE will prevent users from seeing what is behind the forms you present to them. It will compile the code, making it execute a bit faster also. (probably won't be able to tell though). The MDE uses the same data files (backend db) as your MDB uses.
The only drawback to an MDE is that every update you make to your MDB requires you create a new MDE.
You will need to do the following before creating the MDE --
1. Convert your database to the latest available format (XP and 2003 default to 2000 format: you MUST convert them to XP or 2003 before creating the MDE)
2. In the code environment, Debug > Compile [Your Project]. If it compiles, great. If not, correct any errors.
Also highly advisable if you haven't done it already, define a startup form in Tools > Startup, and hide the database window.
And ALWAYS keep a copy of the original database, for making design changes down the track. The MDE can't be unlocked (at least, not easily).