Why can I not open the applicationhost.config file on 64-bit Windows?
Paraphrased from http://icelava.net/forums/thread/5391.aspx
Under x64 Windows certain paths are designated as 64-bit paths, and a 32-bit process, like Visual Studio, is being redirected by Windows to the 32-bit path at C:\windows\SysWOW64 whenever C:\windows\system32 is referenced. The 32-bit process thinks it is looking at C:\windows\system32\inetsrv\config when it has been given C:\windows\SysWOW64\inetsrv\config; which indeed contain none of those configuration files we are after.
To solve (credit to Robert McMurray)
open a 64-bit command prompt and execute the following commands:
This effectively renames the 32-bit config directory so a symbolic link of that name can take its place to redirect back to the 64-bit path which we are really interested in.