if it’s a simple permissions failure (which it is) – just find out which account is trying to do what. 🙂 Download and run procmon (http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx). Filter its trace to only show file events in the d:\inetpub\wwwroot\ folder and then watch for the failure. If something is trying to access d:\inetpub\wwwroot\web.config and getting denied. Procmon will tell you a) which process tried, b) which account it tried as and c) what it tried to do.