IIS / Windows 10: Aspnet_regiis.exe is dead.

The initial error (which does not involve aspnet_regiis – that was an attempt at a solution) , seen when browsing to a Windows Service:

HTTP Error 404.3 – Not Found The page you are requesting cannot be served because of the extension configuration. If the page is a script, add a handler. If the file should be downloaded, add a MIME map.

On the path to fixing this, I came across mention of aspnet_regiis.exe. However attempts to execute that returned this:

This option is not supported on this version of the operating system. Administrators should instead install / uninstall ASP.NET 4.5 with IIS8 using the “Turn Windows Features On/Off” dialog, the Server Manager management tool, or the dism.exe command line tool.

Attempts to firstly use DISM.exe as I prefer the command line approach failed with this:

You cannot service a running 64-bit operating system with a 32-bit version of DISM.
Please use the version of DISM that corresponds to your computer’s architecture.

Googling the above shows that this is a complete red herring (64 vs 32 bit). So I abandoned that and went for the GUI option:

After an iisreset (not clear if I needed to do that), I got the result I wanted, this:

Coming back to aspnet_regiis, I don’t know if this had been removedĀ earlier than Windows 10/WS 2012 R2.