[Source] The 'Microsoft.Jet.OleDb.4.0' provider is not registered on the local machine.

Today I started migrating one of my clients website to a new 64 bits server (Windows server 2008 / IIS7), the website was previously hosted on a 32 bits server (Windows server 2003 / IIS6).

Everything went well, except that a page doing some xlsx “xcell files” parsing is returning an error:
The 'Microsoft.Jet.OLEDB.4.0' provider is not registered on the local machine.

I have already installed the Office 2007/2010 Jet drivers, but if you are having the same problem, the first thing to do is to install it:
http://www.microsoft.com/download/en/details.aspx?id=13255

If you’re still getting the same error like me, then you’ll have to allow the IIS application pool to run 32 bit applications :

Navigate to Server Manager > Roles > Web Server (IIS) > Internet Information Services (IIS) Manager, then right-click on your website’s Application Pool and click “Advanced Settings”:



Set the Enable  32-Bit Application to TRUE.