Virtual Machines can be useful for certain functions, and to solve problems without risking your main OS. But there is fundamentally, no saving of HD space. If, however, it is only the intention to run a bare OS for problem solving then, of course, without any third party add-ons, it is a little smaller than the original. Remember a virtual machine also uses memory (RAM) when they are running. But, as well as the straightforward help factor, they can be used for several useful functions. 1. Software inside a virtual machine, will not affect anything on the host machine – including viruses. This can allow you to install doubtful software and test it for virus, or other, problems. 2. Ditto for Hardware. You can plunge in and check the workability of new drivers, etc., in your VM, before ruining your Host machine. 3. In the same token, software which is known to conflict, can be tested out on a VM and, possibly, have conflictions resolved. 4. One use, which I have used, is in the building, or altering, of websites. You can play with these, ad infinitum, until you are completely satisfied with the result. 5. It is possible to setup several VMs, and increase your skills in using a network, by connecting between them. There is quite a Ram penalty through this usage, however. Keep in mind that anything you run inside a VM, and including the VM itself, incurs a greater penalty on the use of your Computer resources, including Hard disk space.. I have had occasion to use VMs, but my preferred suicidal method is to have a real, second OS installed, and play with that. With a solid backup image, any fatal mistakes are quickly resolved. The drawback, of course, is that, on those occasions when you are experimenting with something potentially hazardous, you do need to reboot into your second OS.