The difficult I do immediately, the impossible takes a little bit longer.
Click the ‘Add new location…’ button (see C)...
And finally, browse (see D) to your location and select ‘OK’. Repeat until you have added all your Trusted Locations. (If you want to add the Subfolders in that folder, don’t forget to check the ‘Subfolders of this location are also trusted' (see E). Click 'OK' until you have closed out of all menus.
When opening your database you get...
Note: The Menu below is from Access 2010. If you are using Access 2007 you will not see *all* of these options. However, the Trust Center options are the same...
Access 2010 Users only...
If you want to allow databases that are stored on the Network Shared to be trusted then check this box. (Mine was checked by default but best to check it.) If not you can Disable AND Clear previously trusted files.
How to use Windows System Colors (Access 2003 and earlier)
Where are the Options? (Access 2007 and higher)
Export Specifications (Access 2007 and higher)
Import Specifications (Access 2007 and higher)
Navigation Pane Options (Access 2007 and higher)
Special Note: You should also check Folder Permissions, especially, if it turns out your database is in a Trusted Location! Your Users will need need Full (Read/Write/Delete) Permissions to the folder where the backend resides.
Object Designers (Access 2007 and higher)
Set Subdatasheet to None (Access 2003 and higher)