Guidance on Windows install re "Add to PATH"

Updated "Installing Rust" and "After installation" to provide additional
guidance to Windows users on including Rust in the Path system variable.

Author: Dangthrimble

src/doc/trpl/installing-rust.md

@@ -2,7 +2,7 @@
 
 The first step to using Rust is to install it! There are a number of ways to
 install Rust, but the easiest is to use the `rustup` script. If you're on Linux
-or a Mac, all you need to do is this: 
+or a Mac, all you need to do is this:
 
 > Note: you don't need to type in the `$`s, they just indicate the start of
 > each command. You’ll see many tutorials and examples around the web that
@@ -25,6 +25,12 @@ $ sh rustup.sh
 [insecurity]: http://curlpipesh.tumblr.com
 
 If you're on Windows, please download the appropriate [installer][install-page].
+**NOTE:** By default, the Windows installer will not add Rust to the Path system
+variable. If this is the only version of Rust you are installing and you want to
+be able to run it from the command line, click on "Advanced" on the install
+dialog and on the "Product Features" page ensure "Add to PATH" is installed on
+the local hard drive.
+
 
 [install-page]: http://www.rust-lang.org/install.html
 
@@ -87,6 +93,11 @@ rustc 1.0.0 (a59de37e9 2015-05-13)
 
 If you did, Rust has been installed successfully! Congrats!
 
+If you didn't and you're on Windows, check that Rust is in your Path system
+variable. If it isn't, run the installer again, select "Change" on the "Change,
+repair, or remove installation" page and ensure "Add to PATH" is installed on
+the local hard drive.
+
 This installer also installs a copy of the documentation locally, so you can
 read it offline. On UNIX systems, `/usr/local/share/doc/rust` is the location.
 On Windows, it's in a `share/doc` directory, inside wherever you installed Rust
@@ -101,5 +112,5 @@ resources include [the user’s forum][users], and
 
 [irc]: irc://irc.mozilla.org/#rust
 [mibbit]: http://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust
-[users]: http://users.rust-lang.org/ 
+[users]: http://users.rust-lang.org/
 [stackoverflow]: http://stackoverflow.com/questions/tagged/rust