VirtualBox, Vagrant, Ruby, and Git have all gone through upgrades (major and minor) since I wrote the chapter on installing them in Multi-Site Drupal. While this hasn't made much of a difference for Mac and Linux/UNIX, Windows 7 support is now much better.
Here is a guide for installing the Multi-Site vagrant image for Drupal 7 on Windows 7. (If you're interested in running Drupal Vagrant, these instructions will work for that project as well.)