Jet Red is the internal Microsoft name for the Jet database engine used by Access. There is/was also Jet Blue, which was used as the database engine for Exchange 4.0 and 5.0. Exchange 5.5 and later use a SQL Server-derived database engine (called ESE97 by Exchange 5.5, ESENT by Windows 2000 Active Directory, and ESE98 by Exchange 2000 - I think ESE stands for Enterprise Storage Engine).
It appears that Jet Red isn't going to be ported to 64-bit Windows, so you'll have to find an alternative for your 64-bit applications (MS would suggest SQL Server or the SQL Server Desktop Engine, known as MSDE). Personally, I think there's still room for an in-process database engine which accesses a single file as a database, although it should be possible to build this from SQL Server components if MS is so inclined.