I have a fault regarding IIS 7.5 on Win Server 2008 R2, whenever I try to change any site bindings or start an application pool I get the error below:

Filename: \\?\C:\Windows\system32\inetsrv\config\applicationHost.config
Error: Cannot write configuration file

the application pools run as network service. None of the sites that are running have been affected however their configuration cannot be changed

UPDATED 05/10/2012

A reboot fixed this issue, however I am curious to know what caused it in the first place.

UPDATE 09/04/2013 The server is no longer in production.

  • 1
    Have you checked the permissions on the applicationHost.config file? – Bernie White Oct 4 '12 at 21:47
  • Yes the permissions where fine, but I am still interested in any answers as to the cause. – flumeware Oct 5 '12 at 15:38
  • 2
    In my case, the server had run out of free space, and freeing up space fixed the problem. – Alexander Puchkov May 13 '15 at 16:27

I had the same problem - turned out we'd just run out of disk space.


App Fabric can cause a Issue like that:


  • Thanks for the info, however app fabric is not installed. Please see comments on above question, the question is no longer relevant to me. – flumeware Apr 9 '13 at 16:35

Have you had any changes to your virus protection policy lately? The actual file that can't be written to is at c:\users\\AppData\Local\Temp\iisexpress. I had our security team re-open access to that directory, just for developers and that fixed it.

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