IIS stores most of your website configuration in the applicationHost.config file. When performing repetitive tasks it’s often quicker and easier to apply changes directly to the applicationHost.config file rather than via the IIS manager user interface.
The applicationhost.config file can be found here: %windir%\System32\inetsrv\config\applicationHost.config
Here’s one little gotcha that can catch out even seasoned administrators or developers off – don’t use a 32 bit text editor on a 64 bit OS!
Well it turns out that if you use a 32 bit text editor on a 64 bit platform, you are actually modifying the %windir%\SysWOW64\inetsrv\Config file instead! What! This isn’t immediately apparent because the text editor thinks it’s accessing the correct file, but it isn’t! To explain why this is the case lets take a step back …
If you don’t believe me try it for yourself … after modifying the applicationHost.config file using a 32 bit text editor, you should see the change appear in the %windir%\SysWOW64\inetsrv\Config\applicationHost.config file. Weird hey 🙂
What's Going On Here!
Windows 32 bit applications running on 64 bit OS's require an emulation layer (known as WOW64) to provide backward compatibility with the newer platform. All this ‘magic' is largely handled by the operating system and is mostly transparent to the underlying application.
If you're interested in all the technical details, you can find more information here.