A family of Microsoft relational database management systems designed for ease of use.
The most recent version of Access allow you to open/use only the latest MDB file format. So if yours is a 2000, 97, 2.0, ... MDB then the newer version are incompatible and you must first use an intermediary version of Access (I typically recommend 2010) to upgrade the file format. The newer ACCDB file format had been out for 15+ years now, it should be a priority for any developer to upgrade MDBs to this format to ensure the longevity of their application.