Often during troubleshooting we need to figure out the locations of all the web.config files that could potentially affect a web application. With IIS 7.0 the configuration is now decentralized and settings could be spread out over a bunch of config files.
Appcmd provides an easy way to locate all the web.config files that affect IIS / ASP.NET settings.
appcmd search config
This will list all the locations that IIS would read for a config file including all virtual directories under a website. The best part is that it also scans physical folders that are not marked as applications.