Spoiler alert!: IIS keeps history of config files!
Well, Somethings wrong!
2 days ago, I helped the customer deploy their new Exchange 2013. Everything is fine then, we had OWA and ECP running. Today I was called because they decided to add new mailboxes and cant access the ECP.
As troubleshooting, I opened the IIS Management Console and was presented with this:
Opened the File and this came up. My reaction: What’s this!? Config files for aliens?!
More background first for troubleshooting:
1. Client Installed .NET Framework 3.5 and ASP.NET 3.5 thinking this is missing.
2. Client Restarted everything. Yea, the have you tried turning it on and off again.
So le me, going back to the original problem: the Config file is corrupt!
Good guy IIS, always create a copy of the config history under INETPUB! So I just go to that folder and under the second to the last CFG History I copied the applicationhost.config.
Now go to The Inetserv Config folder under System32 (as the error said and rename the applicationhost with .old so that you have a backup copy of it. Then paste the applicationhost.config here.
Back to work now and Happy deployment!