title: rails server doesn't start - Error messages
body: <p>I just installed the railsinstaller on my Windows 7. I created a sample_app folder inside my C:/Sites. I updated everything with "gem update". When I want to start a server, I got the following error:</p>
  
  <pre><code>Lanti@LANTI-PC /c/Sites/sample_app
  $ rails s
  c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/execjs-2.2.1/lib/execjs/run
  times.rb:51:in `autodetect': Could not find a JavaScript runtime. See https://gi
  thub.com/sstephenson/execjs for a list of available runtimes. (ExecJS::RuntimeUn
  available)
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/execjs-2.2.1/lib/execjs.rb:5:in `&lt;module:ExecJS&gt;'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/execjs-2.2.1/lib/execjs.rb:4:in `&lt;top (required)&gt;'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/uglifier-2.5.3/lib/uglifier.rb:3:in `require'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/uglifier-2.5.3/lib/uglifier.rb:3:in `&lt;top (required)&gt;'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/bundler-1.7.3/lib/bundler/runtime.rb:76:in `require'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/bundler-1.7.3/lib/bundler/runtime.rb:76:in `block (2 levels) in require'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/bundler-1.7.3/lib/bundler/runtime.rb:72:in `each'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/bundler-1.7.3/lib/bundler/runtime.rb:72:in `block in require'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/bundler-1.7.3/lib/bundler/runtime.rb:61:in `each'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/bundler-1.7.3/lib/bundler/runtime.rb:61:in `require'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/bundler-1.7.3/lib/bundler.rb:133:in `require'
      from c:/Sites/sample_app/config/application.rb:7:in `&lt;top (required)&gt;'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands.rb:76:in `require'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands.rb:76:in `block in &lt;top (required)&gt;'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands.rb:73:in `tap'
      from c:/RailsInstaller/Ruby2.0.0/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands.rb:73:in `&lt;top (required)&gt;'
      from bin/rails:4:in `require'
      from bin/rails:4:in `&lt;main&gt;'
  Lanti@LANTI-PC /c/Sites/sample_app
  $
  </code></pre>
  
  <p>Here is the list of my installed gems:</p>
  
  <pre><code>Lanti@LANTI-PC /c/Sites/sample_app
  $ gem update
  Updating installed gems
  Nothing to update
  Lanti@LANTI-PC /c/Sites/sample_app
  $ gem list
  
  *** LOCAL GEMS ***
  
  actionmailer (4.1.6, 4.0.0, 3.2.14)
  actionpack (4.1.6, 4.0.0, 3.2.14)
  actionview (4.1.6)
  activemodel (4.1.6, 4.0.0, 3.2.14)
  activerecord (4.1.6, 4.0.0, 3.2.14)
  activerecord-deprecated_finders (1.0.3)
  activerecord-sqlserver-adapter (4.1.0, 3.2.12)
  activeresource (4.0.0, 3.2.14)
  activesupport (4.1.6, 4.0.0, 3.2.14)
  arel (5.0.1.20140414130214, 4.0.2, 3.0.2)
  atomic (1.1.16, 1.1.10)
  bigdecimal (1.2.5, 1.2.0)
  builder (3.2.2, 3.1.4, 3.0.4)
  bundler (1.7.3, 1.3.5)
  coffee-rails (4.0.1, 4.0.0)
  coffee-script (2.3.0, 2.2.0)
  coffee-script-source (1.8.0, 1.6.3)
  erubis (2.7.0)
  execjs (2.2.1, 1.4.0)
  hike (2.1.3, 1.2.3)
  i18n (0.6.11, 0.6.4)
  io-console (0.4.2)
  jbuilder (2.1.3, 1.5.3)
  journey (1.0.4)
  jquery-rails (3.1.2, 3.0.4)
  json (1.8.1, 1.7.7)
  mail (2.6.1, 2.5.4)
  mime-types (2.3, 1.25.1, 1.23)
  minitest (5.4.1, 4.7.5, 4.3.2)
  multi_json (1.10.1, 1.7.7)
  pg (0.17.1 x86-mingw32, 0.16.0 x86-mingw32)
  polyglot (0.3.5, 0.3.3)
  power_assert (0.1.3)
  psych (2.0.6, 2.0.0)
  rack (1.5.2, 1.4.5)
  rack-cache (1.2)
  rack-ssl (1.4.1, 1.3.3)
  rack-test (0.6.2)
  rails (4.1.6, 4.0.0)
  rails-observers (0.1.2)
  railties (4.1.6, 4.0.0)
  rake (10.3.2, 0.9.6)
  rb-readline (0.5.1, 0.5.0)
  rdoc (4.1.2, 4.0.0)
  rubyzip (1.1.6, 0.9.9)
  sass (3.4.5, 3.2.19, 3.2.9)
  sass-rails (4.0.3, 4.0.0)
  sdoc (0.4.1)
  sprockets (2.12.2, 2.11.0, 2.10.0, 2.2.2)
  sprockets-rails (2.1.4, 2.0.1, 2.0.0)
  sqlite3 (1.3.9 x86-mingw32, 1.3.7 x86-mingw32)
  sqlite3-ruby (1.3.3)
  test-unit (3.0.1, 2.0.0.0)
  thor (0.19.1, 0.18.1)
  thread_safe (0.3.4, 0.1.2)
  tilt (2.0.1, 1.4.1)
  tiny_tds (0.6.2 x86-mingw32, 0.6.1 x86-mingw32)
  treetop (1.5.3, 1.4.15, 1.4.14)
  turbolinks (2.3.0)
  tzinfo (1.2.2, 0.3.41, 0.3.37)
  uglifier (2.5.3)
  Lanti@LANTI-PC /c/Sites/sample_app
  </code></pre>
  
  <p>Thank You for your help!</p>