There are many benefits associated with software virtualization, and the majority of Forrester clients have already started their virtualization journey. However, like any licensing metric, the devil is in the details; while buying virtualization can be confusing, staying compliant is the real headache. Sourcing professionals must understand the nuances of virtualization, as well as the different licensing rules and policies applied by different software vendors, if they want to ensure they stay compliant and avoid costly embarrassment at audit time. This report summarizes what virtualization is and gives recommendations on how to stay compliant.