These guest virtual machines can be running a variety of different operating systems that include older versions of Windows, linux, and even MacOS with some tweaking. When using VirtualBox, the software is installed on the host machine and then any other virtual machines are considered guests of that host.

This allows you to run virtually any operating system at the same time while using Windows. Using VirtualBox you are able to install other operating systems into a virtual computer that can be launched and used directly within Windows. VirtualBox is free and enterprise-ready virtual machine platform that allows you to run other operating systems within Windows.