As far as I know in theory 2007 and 2010 should use the same format. But in real life they are different! One problem might be the references in VBA (VBA Windows, Tools, References). If you take a database from a computer with Access 2007 and work on the database in Access 2010 then some of these references are automatically updated to the newer office version (i.e. Microsoft Office 14.0 Access database engine Object Library). And when you try to use this database in Access 2007 again it won’t work because the references are changed. You can easily fix this by changing the reference back to what it was in 2007. I.e. change “Microsoft Office 14.0 Access …” back to “Microsoft Office 13.0 Access …” on the PC with Access 2007. Then at least that problem is solved. This is one of the problems between 2007 and 2010 but there are others which IMHO sometimes matter and sometimes don’t create a problem.