Setting up a host machine (usually a machine with big storage space to hold guest operating systems, and a desktop virtualization platform software to run on top of your host machine). On top of the virtualization platform one or more guest operating systems can be installed. These can run in parallel if enough RAM and resources are available, or can just run one guest O/S at a time. Two very popular solutions out there are: Both platforms enable the creation of virtual hard disks for each guest operating system. This virtual hard disk is stored as a single file with the extension (.ova). Which is a standard for virtual hard disks nowadays.