Oracle - (Free)
VirtualBox is an easy and elegant solution for those who want to control a computer from another computer.
VirtualBox offers virtualize your operating system (OS) guests on a host machine. Called hypervisor, the application supports Windows OS X, Linux, Mac, Solaris, FreeBSD, etc.. as host, Mac OS X missing the call as a guest.
It also includes a remote access via HTTP protocol, convenient for demonstrations on a clean system. The ability to manage multiple states of the system is particularly interesting and its interface is very simple.
Virtualization solutions allow installing an operating system on a virtual machine using the resources of the host PC , thus enjoying very good performance. In the genre, several solutions are known for their ease of use, such as VMware Workstation , Parallels Desktop or Microsoft Virtual PC 2007 SP1.
A virtual machine is a useful way to use two operating systems simultaneously and harmless to the host computer. There is the possibility to install Linux on a virtual machine on Windows and vice versa .