Devkit not recognised

I am running Windows 7 Home Premium.

I have Ruby 1.9.3p362 installed at C:, and DevKit also installed at
C:, thus avoiding spaces in
folder names and paths. The version of DevKit is
DevKit-tdm-32-4.5.2-20111229-1559-sfx.exe
which seems to be the latest one.
According to the installation instructions, I inspected config.yml and
confirmed that it included
the folder for my Ruby installation (I also tried changing the slash to
a Windows-style backslash,
with no effect).
I did the test installation “|gem install rdiscount --platform=ruby”
which gave:-

ERROR: Error installing rdiscount:
The ‘rdiscount’ native gem requires installed build tools.

Please update your PATH to include build tools or download the DevKit
from ‘Downloads’ and follow the instructions
at ‘Development Kit · oneclick/rubyinstaller Wiki · GitHub

John S. wrote in post #1093470:

I am running Windows 7 Home Premium.

I have Ruby 1.9.3p362 installed at C:, and DevKit also installed at
C:, thus avoiding spaces in
folder names and paths. The version of DevKit is
DevKit-tdm-32-4.5.2-20111229-1559-sfx.exe
which seems to be the latest one.
According to the installation instructions, I inspected config.yml and
confirmed that it included
the folder for my Ruby installation (I also tried changing the slash to
a Windows-style backslash,
with no effect).
I did the test installation “|gem install rdiscount --platform=ruby”
which gave:-

ERROR: Error installing rdiscount:
The ‘rdiscount’ native gem requires installed build tools.

Please update your PATH to include build tools or download the DevKit
from ‘http://rubyinstaller.org/downloads’ and follow the instructions
at ‘Development Kit · oneclick/rubyinstaller Wiki · GitHub

You need to compile your Ruby code before you attempt to utilize it for
any type of application, open a cmd. terminal and run the following sets
of process on your version of RoR.

If you already have Ruby installed on your machine, the gem is
accessible via the command line, first get into the .bin folder at the
root of Ruby directory:

C:>cd C:\workfolder\Ruby193.bin

Then run the install snippet:

C:\workfolder\Ruby193.bin>gem install rails

And wait, it will take a minute for this to finish. When it is done,
stay in the .bin file and try running the internal server:

C:\workfolder\Rubuy193\bin>rails server

If there is still any incomplete code compilation that is necessary for
Ruby to act properly she will let you know, such as: “no json <1.7.6>”
or “no sass <2.2.0>” just call the gem installer for each and every one
until there are no more errors. Then run any external support process
you would like to use for building projects in your editor, one by one
through the same process, if you want to include coffeescript or
whatever in a Ruby build then run:

C:\workfolder\Rubuy193/bin>gem install coffeescript

With any gem successfully installed you gain the ability to convert
files into Ruby compatible support structures that will allow her to
function more completely and make use of her deep dynamic control over
the environment.

This is also a good method for experimenting with the syntax and it is
the best way to integrate diverse code into the Ruby environment, but…
you can also place external assets directly into the build path in your
editor, however the Ruby Gem must be installed and compiled from within
the terminal environment for best possible results and I could not
imagine wasting the opportunity to build a complete project bundle for
fluid framing and super clean styling with way fast, very simple
JavaScript, Ruby is a sweet language!