Or maybe you've upgraded to Windows 10 and find a favourite old app doesn't work any more? Create a Windows XP VM and you might be able to run it again. If you'd like a closer look at Windows 10 before you upgrade, for instance, then you could install Microsoft's latest in a VM, then access it in a window on your XP or Vista desktop. It's a powerful capability that has many different applications. Oracle VM VirtualBox is an industrial-strength open source virtualisation tool that makes it easy to create virtual machines (VMs), simulated computers that run on your PC but act as though they were separate systems.