Here are some commands from my Windows 7 command prompt that show the problem. As you can see, I added everything I could think of to my path, trying to solve the problem. Same DevKit had worked for me before with the same Ruby installation, so I think I installed it right.
E:\ruby\bookmarks3Copy>gem install atomic -v '1.1.9'
ERROR: Error installing atomic:
The 'atomic' 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 'http://github.com/oneclick/rubyinstaller/wiki/Development-Kit'
E:\ruby\bookmarks3Copy>path
PATH=f:\ruby\DevKit;f:\ruby\DevKit\bin;[snip];f:\ruby\DevKit\bin;f:\programs\git\bin;"F:\Program Files (x86)\KDiff3"
E:\ruby\bookmarks3Copy>where ruby
f:\ruby\Ruby200-x64\bin\ruby.exe
E:\ruby\bookmarks3Copy>gem list atomic
*** LOCAL GEMS ***
atomic (1.1.14)
E:\ruby\bookmarks3Copy>bundle list atomic
DL is deprecated, please use Fiddle
f:/ruby/Ruby200-x64/lib/ruby/gems/2.0.0/gems/atomic-1.1.14
i can share you my solution here,hope it may works
pik list
It should show you
187: ruby 1.8.7 (2010-08-16 patchlevel 302) [i386-mingw32] 192: ruby 1.9.2p290 (2011-07-09) [i386-mingw32] 193: ruby 1.9.3p327 (2012-11-10) [i386-mingw32]
200: ruby 2.0.0p247 (2013-06-27) [i386-mingw32] If its not pointing to ruby version 200 then
pik use 200
ruby dk.rb install It will enhance DevKit to your installed Rubies
Finally gem install rails
This will install latest rails version 4 for Ruby 2.0