Vagrant is a collection of scripts written in Ruby to manage VirtualBox images in a shared environment (like the QA boxes inside a company): install them, update them, etc. Unfortunately installing it under Windows is not as straight forward as one would want, so here are some useful tips:

• Read the Windows setup page and the Windows x64 setup page (if you are on 64 bit)

If you are on a 64 bit Windows install:

• Check out this post if your JRuby is using the 32 bit JVM on a x64 Windows setup
• You need to use version 4.0 of VirtualBox (rather than the latest). You can get it from here
• You need to use an older version of Vagrant:

  jgem install jruby-openssl jruby-win32ole
  jgem install --version '=0.7.8' vagrant

• If the vagrant box download stops around 4G, check that you have a NTFS filesystem (rather than FAT) and deactivate any "network" scanning capabilities of installed security software (I had problems with NOD32 particularly)

HTH