The 'Microsoft.Jet.OLEDB.4.0' provider is not registered on the local machine.

I encountered this error when installing a client's website on my server. The underlying problem is that the application pool only runs 64-bit code by default and there isn't a 64-bit OLEDB driver for the Jet database.

To resolve the issue, in the application pool's settings change Enable 32-Bit Applications to True.