It makes a long time that I didn't speak about virtualisation… However it is a subject which will be discussed more and more . Moreover the RedHat company has just announced the nearest installation of technology XEN within its version for professional. Contrary to other technologies of virtualisation such VMWare or Qemu which simulates the material and the bios, the virtual machines under XEN has access to the material thanks to XEN modified kernel. The result of this other paradigm is a virtual machine almost as fast as the machine host. So enjoy the virtualization!!! The only constraint is that the architecture of the virtual machines must enable them to use the technology XEN… contrary to VMWare and Qemu which does not require modification of “guest” OS. It is not a problem with opensource OS such Linux, whose code was already modified to be able to turn with XEN, on the other hand what is at stake is Windows… And it is there that the real difficulty arises: much user of Linux uses a virtual machine to make turn Windows, even if the team of XEN said to have modified Windows to allow to make it turn under XEN, some licences prevent the team from publishing… Let us hope that the agreement between Microsoft and XEN could change the situation. In addition the arrival of dual the core and technologies of virtualisation directly within the processors should end licence's problems mentioned herebefore and another side to still improve quality of virtualisation… The bootloader could thus belong very soon to last and the stories of I am under such OS, I must reboot… will be finished soon.