impersonate in Web.config in subfolder does not work.

Hi experts,
I'm facing a problem with the current setup of my application. The basic idea is that some folders have been made writeable and we have a couple admin pages to handle the changes there.
All admin pages are in an "Admin" subfolder of the application. So we added in the Admin subfolder the following Web.config file:
<configuration>
<system.web>
<identity impersonate="true" userName="ourSpecialUser" password="ourSpecialPassword" />
</system.web>
</configuration>
FYI: the root Web.config has <identity impersonate="false" ...