oracle virtualbox 5 doesnt support windows 10 hosts and guests yet
Please be aware that Windows 10 is not yet officially supported! There are known problems with VirtualBox 5.0 on Windows 10 hosts and with Windows 10 guests. Some of the problems are fixed in the most recent test build which can be found here
Jailtime.org have Linux distributions that can run as Xen guests out of the box, obviating the need to create your own custom filesystems. The filesystems on this site have already been tweaked to deal with Xen’s idiosyncracies, and are also designed to be lightweight and minimally divergent from the original distribution.
The Google App Engine JumpBox gives you a drop in place system for doing Google App Engine development that’s contained in an isolated environment within a virtual machine.
It runs exactly the same on GNU/Linux, Mac and other OS’s and gives you a development environment that lets you take advantage of great virtualization features like snapshots. It will run from a single download on Parallels Desktop, VMWare, Virtual Iron, Xen Open Source in fully virtualized mode and others.