Symptoms
When you use FileMon or another utility to monitor file activity, if an application uses DAO 3.6x with Jet 4.0, you receive the following error message:

FILE NOT FOUNDfor the following dynamic-link libraries (DLLs):
MSJET49.DLL
MSJET48.DLL
MSJET47.DLL
MSJET46.DLL
MSJET45.DLL
MSJET44.DLL
MSJET43.DLL
MSJET42.DLL
MSJET41.DLLHowever, you also notice that MSJET40.DLL is loaded successfully.
Resolution
This behavior is by design to allow future Jet 4 functionality to be included into DLLs that are named incrementally. For example, a new version of Jet 4 can be implemented in a DLL named MSJET41.DLL. DAO 3.60 then automatically uses the new version of Jet 4, MSJET41.DLL.
Microsoft Development has found that it does not significantly impact DAO 3.60 or Jet 4.0 performance to load these DLLs.