This morning I ran into a problem when running a repair on my broken SharePoint installation.  Everything seemed to be going well until the setup needed to restart the World Wide Web Publishing service (IIS).  The error message was rather cryptic, say that it might be due to my login account not having service start permissions – but I know I have.

Debugging step 1:  Look in the windows services list and see if I can manually start the service. This was a little more helpful as it told me it couldn’t start due to a dependency not starting.

Debugging step 2: Check the service dependencies.  It appears that the Windows Process Activation service (WAS) wouldn’t start, although it only returned the message “Error 13: The data is invalidâ€?.

Debugging Step 3: Check the system event log.  Here I found the most helpful message so far:

The Windows Process Activation Service encountered an error trying to read configuration data from file ‘\\?\C:\Windows\system32\inetsrv\config\applicationHost.config’, line number ’0′.  The error message is: ‘Configuration file is not well-formed XML’.  The data field contains the error number.

It seems that at some point the applicationHost.config got trashed.  Luckily, when you make changes to web applications in IIS it creates a backup of the applicationHost.config file in c:\inetpub\history.  All you need to do is copy a good copy from the history and put it into c:\windows\system32\inetsrv\config.

And Roberts your mothers brother, WAS starts, IIS starts and the repair of SharePoint can continue!

ps. I’m running IIS7 on Windows 2008 Server.