Pieces You Need

* Ruby
* RubyGems
* Rails (Gem)
* A Database Engine

Install Ruby and RubyGems

Get the latest One-Click Ruby Installer, current version 1.8.6-26. Run this, and select all the defaults. This will install Ruby under C:\ruby, and install RubyGems for you. The README at the end of the installation will show you all the versions of each piece that it installed. You need to update gems after installation: