VirtualBox is an Open Source virtualization tool that allows you to run Linux under Windows and viceversa.
VirtualBox has an extremely modular design with well-defined internal programming interfaces and a client/server design.
With VirtualBox, you can install any version of an operating system, such as Linux, Solaris, and other versions of Windows and run them within your current version of Windows.
VirtualBox is available on all the major operating systems.
VirtualBox also has three additional enhancements for the latest version and these include Virtual USB controllers, Remote Desktop Protocol and USB over DRP.
If you don’t want to pay for commercial solutions and require a virtual OS for generally minor usage, VirtualBox is more than enough.