I came across a nasty issue when i installed the Advanced Logging feature for IIS7 via the Web Platform Installer on my Windows 2008 Server.  Basically, after installation and reboot none of my sites were working and returned 503 – Internal Server Error.

Snooping around in the Event Viewer i found the following error reported by the W3SVC…

The Module DLL C:\Program Files\IIS\Advanced Logging\AdvancedLoggingModule.dll failed to load.  

The data is the error

Even though the DLLs are there, it is not picking them up.

I managed to find a fix via google that involves editing the configapplicationHost.config file in the C:\Windows\System32\inetsrv\ directory.

1.  Copy AdvancedLoggingModule.dll and ClientLoggingHandler.dll to %windir%\system32 (C:\windows\system32  on a default setup)

2.  Locate the file C:\Windows\System32\inetsrv\configapplicationHost.config and make a backup, then open it in a text editor (i recommend Notepad++).

3.  Search for the following 2 lines (mine are located on line 570)..

<add name="ClientLoggingHandler" image="%ProgramFiles%\IIS\Advanced Logging\ClientLoggingHandler.dll" />
<add name="AdvancedLoggingModule" image="%ProgramFiles%\IIS\Advanced Logging\AdvancedLoggingModule.dll" />

and alter them to….

<add name="ClientLoggingHandler" image="%windir%\system32\ClientLoggingHandler.dll" />
<add name="AdvancedLoggingModule" image="%windir%\system32\AdvancedLoggingModule.dll" />

4. Open a command prompt and run iisReset.

5. All sites should now be working.