Utilizing Virtual Machines for Different Operating System Installs in a Secure Manner

Discuss three situations for uses of different operating system installs in a virtual environment while at the same time securing the operating system installation. For example, think about why a system administrator would install several different versions of Microsoft Windows VM's? Or maybe a developer installing different distributions of Linux? Think about the different IT departments an organization may have and what can be done to save time, money, and resources when they utilize virtual machines.