Installing DevExpress controls apparently this problem you get with Telerik controls (RadControls) as well on a 64-bit machine and running the examples that use Access as its database may cause the following error above even if you have the Microsoft.Jet.OLEDB.4.0 provider installed.
This problem comes from the fact that the MS Jet engine (the DB engine behind Microsoft Access) does not have a 64-bit port. Running on a 64-bit machine will default to a 64-bit web application pool and it will not be able to find the 32-bit version of the Jet engine component.
The solution is to configure the application pool and enable 32-bit application support. For IIS 7, running on Windows 7, you can do this from the application pool’s advanced settings dialog: