machine.config

...is another .config file in the ASP.NET Framework like Web.config. It can effect how your web site runs just like Web.config and is 32-bit or 64-bit specific living at a path such as:

C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config

 
 

Anymore, you're going to have to go out of your way to run the 32-bit version in IIS.