Microsoft has no plans to natively support Jet under 64-bit versions of Windows.

The Jet Database Engine will remain 32-bit for the foreseeable future. Microsoft has no plans to natively support Jet under 64-bit versions of Windows. This means that native 64-bit applications (such as the 64-bit versions of SQL Server) cannot access data stored in MDB files through ODBC, OLE DB, or any other means, except through intermediate 32-bit software (running in WoW64) that acts as a proxy for the 64 bit client.[9]

 

Windows 2008 includes the latest version of Jet - however, it's still only
32-bit (there is no 64-bit version of Jet that I am aware of). The 64-bit
SP8 for Jet 4 for Windows 2003 is the same installer that runs on the 32-bit
OS versions too - the 64-bit in the KB article name is irrelevant, it's just
there for those users who have 2003 64-bit.