I have had multiple experiences with the following question…So I knew I should post it.

Greg (Awesome IT Guy) emailed me this:

"When I open a MDB created in Access 2003, that has code in it, In Access 2007, security disables the code. How do I set security to allow code as default?"

The answer is "Trusted Center" and "Trust Center Settings."
(Office Button–Access Options)

Most people are missing the security part and thinking that the database has been upgraded and ruined…Keep an eye out for this flag:

You have to enable the content by clicking the Options button.

(Don’t do this if you don’t where it came from, or were not expecting it, etc…You are enabling code).

Now back to the matter at hand: Setting up a Trusted Location

Hit the Trust Center Settings (see image below)

You can just click "Open the Trust Center"

Click Trusted Locations (Second on the List) and then press function key "F1".

Between your company policies and your help menu you should be able to determine the appropriate security options.