Microsoft scrubbed the direct links around 2018. If you go to the official download center and search for "Jet 4.0," you will likely land on a page for "Microsoft Access 2000 Database Engine" (obsolete) or the "Microsoft Access Database Engine 2016 Redistributable" (which is ACE, not Jet).
Here is the trick: The 2010 version (ACE 14) maintains the best backward compatibility with Jet 4.0. It reads MDBs better than the 2016 or 2019 versions. You download the 32-bit version ( AccessDatabaseEngine.exe ), install it, and use the connection string: Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\oldfile.mdb;Persist Security Info=False;
Microsoft killed Jet 4.0 for good reason. It was fast, but it was fragile.
