Because neither DAO 3.0 or DAO 3.5 are thread-safe. A web server (such as IIS) will always spawn different threads and load the ISAPI DLL in the context of the thread. The ISAPI DLL is then talking to the BDE which talks to the DAO engine (not thread-safe). So, if you need to write an ISAPI/NSAPI DLL talking to Access 95/97 tables, you'll need to use Microsoft's ODBC driver. The ODBC driver doesn't use the DAO engine, and is thread-safe.