From Techthrob.com: Virtualization is the technique of running a "guest" operating system inside an already-running OS; for example, Windows inside Linux, or visa-versa. This article compares four virtualization products available for Ubuntu Linux: the free, open source Qemu; the closed-but-free versions of VirtualBox and VMware-Server, and the newly-available, commercial Parallels. Read More at Techthrob.com