The success of cloud computing would not be possible without the advances in virtualization. The basic concept is to have one resource pretend to be another. Its implementation is applicable to many areas of computing. Virtualization allows a computer to become several different computers, or one software package to emulate another. Although virtualization technology has been around for many years, it is only now beginning to be fully deployed. One of the reasons for this is the increase in processing power and advances in hardware technology. As the benefits of virtualization are realised, we can observe the benefits to a wide range of users, from IT professionals, to large businesses and government organizations. Firstly this paper aims to discuss Virtualisation Tecnology, secondly analyse current risks during migrating to virtual environment, and finally propose corresponding counter measures in order to facilitate the migration to Virtual Environment.