Xensource's Xen 3.0 began as an open source software project that started at the University of Cambridge. Xen is meant to virtualize operating system (OS) instances with abilities enhanced beyond those of current choices, such as VMwares products. Instead of re-creating a machine within which any OS can run, Xen allows whole operating systems (OSs) to run atop Xen, if their kernels have been modified to do so. This para-virtualization approach decreases the flexibility of the VMware OSs, and Xen cannot run currently with Windows. However, reduced overhead from running virtualized instances, in addition to the project's free GNU GPL (General Public License), have gotten considerable attention. Xen seems to be a good bet for the future, but presently issues remain unclear. The next major release, which is Xen 3.0 and follows Xen 2.0.7, has been delayed for months. Xen 3.0 will support Advanced Micro Devices AMD64 architecture, symmetric multiprocessing, guest OSs, and a set of other features that can be seen at cl.cam.ac.uk/Research/SRG/netos/xen/roadmap.html. Xen can run with Linux or NetBSD as its host OS and can support Linux, NetBSD, and FreeBSD guests. Among vendors citing Xen in promotions as their future virtualization choice are Red Hat and Novell. Xensource is a company founded to make Xen technology a commercial product, but has not yet released any services or products. Hardware platform additions from Intel and AMD could allow the Xen approach to run with unmodified OSs such as Microsoft Windows, but for Xen to realize its potential, it will need solid participation from Linux distributors and will also need much improved packaging and integration for creation, running, and management of instances.