Xen is a free software virtual machine monitor for IA-32, x86-64, IA-64 and PowerPC architectures. It runs on a host operating system and allows several guest operating systems to be run on top of the host on the same computer hardware at the same time. Modified versions of Linux, NetBSD and Solaris can be used as hosts. Several modified Unix-like operating systems may be employed as guest systems; on certain hardware, as of Xen version 3.0, unmodified versions of Microsoft Windows and other pro