You're confusing two separate concepts. MDE files are compiled versions of MDB files. They have all source code removed, and they're a good way to protect your code from tampering or piracy. Access Runtime is a separate version of Access that allows users to open Access databases (MDB, MDE, etc.) without needing to buy a full copy of Access. Prior to the 2007 version, developers had to buy a separate license to be able to distribute the Runtime version of Access. As of Access 2007, Microsoft is providing the Runtime version for free.