I have recently been working with a customer who had a half implemented Exchange 2013 infrastructure but were suffering issues where no client could connect. After a little investigation the World Wide Web Publishing Service would not start due to a dependency failure on the Windows Process Activation Service.Looking at Event Log I could see WAS logging a 5005, 5036 and finally a 5172 Error. The 5172 Error text is as follows:[error]The Windows Process Activation Server encountered an error trying to read configuration data from file ‘\?\\C:\Windows\System32\inetsrv\config\applicationHost.config’, line number ‘1’. The error message is: ‘Configuration file is not well-formed XML’. The data field contains the error number.[/error]A quick look in the file specified shows that it is completely empty, so that explains the ‘not well formed’ part but what should it be?Well historical copies are stored by default in C:\inetpub\history\CFGHISTORY_xxxxxxxxxx so find the newest folder and in there you will find a copy of the ApplicationHost.config file. Simply copy the file from this history folder to the location in the error message and start the Windows Process Activation Service.