Checklist to help Windows users

* Addresses observation in elmbridge#100

Introduction.md

@@ -28,7 +28,7 @@ At various points today, you'll also be asked to download code from GitHub, so i
 
 ### Installing Elm
 
-If you haven't done so already, follow [the official Elm guide](https://guide.elm-lang.org/get_started.html) for installing the language platform.
+If you haven't done so already, follow [the official Elm guide](https://guide.elm-lang.org/get_started.html) for installing the language platform. **Note for Windows users:** You might want to check our [handy Windows installation checklist](Special Installation Notes.md) to guide you through installation.
 
 You can verify everything is working by launching the Elm REPL ([What is a REPL?](https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop)) by running the following command in your terminal:
 

SUMMARY.md

@@ -7,6 +7,7 @@
 * [Getting Started](Getting Started.md)
 * [The Basic Building Blocks of Elm](The Basic Building Blocks of Elm.md)
 * [Intermission: Building User Interfaces](Building User Interfaces.md)
+* [Special Installation Notes](Special Installation Notes.md)
 
 ## Making an Emoji Translator
 

Special Installation Notes.md

@@ -0,0 +1,19 @@
+# Installation Notes for Windows Users
+
+If you are running Windows on your machine, you might find this checklist of activities helpful:
+
+* Before running the Windows installer, shut down your command prompt (`cmd.exe`) and/or Cygwin applications.
+* After running the installer, you will also need to install `nodejs`, from the [Node JS](https://nodejs.org/) website. You can choose the option that says "Recommended For Most Users."
+* After completing the NodeJS installation, open a new command prompt (or Cygwin) window and type in `elm-repl` at the command line. If you _don't_ see this message, you are good to go! If not, consult an instructor or TA:
+
+```
+$ elm repl
+The REPL relies on node.js to execute JavaScript code outside the browser.
+I could not find executable 'node' or 'nodejs' on your computer though!
+
+You can install node.js from <http://nodejs.org/>. If it is already installed
+but has a different name, use the --interpreter flag.
+---- elm-repl 0.17.1 -----------------------------------------------------------
+ :help for help, :exit to exit, more at <https://github.com/elm-lang/elm-repl>
+ --------------------------------------------------------------------------------
+```