IIS cannot run unpacked web app

I have unpacked a web application in a folder. It contains dll's, configuration files and the wwwroot directory. Then I have created an IIS web application pointing to the previous folder. When I browsed the page I got a HTTP Error 500.19 - Internal Server Error. The error code is 0x8007000d. Then I clicked on "View more information" and it says that either ApplicationHost.config or the Web.config file contain a malformed XML element. The problem is that my Web.config file does not contain malformed elements and I do not have a ApplicationHost.config file in my folder.