I installed EventSentry on a 64-bit version of Windows and when trying to access the web reports I get the following error: "Provider is not specified and there is no designated default provider". I would like to use the Microsoft Access database.

Microsoft has not yet provided 64-bit drivers for Microsoft Access, and at this point does not seem to have any plans of doing so.

While the EventSentry agent is able to write to Access database (using the default EventSentry Access System DSN) since it is a 32-bit application, the web reports using IIS are not able to access this DSN as IIS was ported to be a native 64-bit application.

You will either have to switch to a database that offers both 32-bit and 64-bit ODBC drivers (e.g. Microsoft SQL Server) or install and setup IIS on a 32-bit machine.