What Is a Virtual Machine?

A virtual machine is a program that acts as a virtual computer. It runs on your current operating system – the “host” operating system – and provides virtual hardware to “guest” operating systems. The guest operating systems run in windows on your host operating system, just like any other program on your computer. The guest operating system runs normally, as if it were running on a physical computer – from the guest operating system’s perspective, the virtual machine appears to be a real, physical computer.

Virtual machines provide their own virtual hardware, including a virtual CPU, memory, hard drive, network interface, and other devices. The virtual hardware devices provided by the virtual machineare mapped to real hardware on your physical machine. For example, a virtual machine’s virtual hard disk is stored in a file located on your hard drive.

You can have several virtual machines installed on your system; you’re only limited by the amount of storage you have available for them. Once you’ve installed several operating systems, you can open your virtual machine program and choose which virtual machine you want to boot – the guest operating system starts up and runs in a window on your host operating system, although you can also run it in full-screen mode.

Uses For Virtual Machines

Virtual machines have a number of popular uses:

• Test new versions of operating systems: You can run the development version of Windows 8 in a virtual machine on your Windows 7 computer. This allows you to experiment with Windows 8 without installing an unstable version of Windows on your computer.


• Experiment with other operating systems: You can install various distributions of Linux and other more obscure operating systems in a virtual machine to experiment with them and learn how they work. If you’re interested in Ubuntu, you can install it in a virtual machine and play with it at your own pace — in a window on your normal desktop.

• Use software requiring an outdated operating system: If you’ve got an important application that only runs on Windows XP, you can install XP in a virtual machine and run the application in the virtual machine. The virtual machine is actually running Windows XP, so compatibility shouldn’t be a problem. This allows you to use an application that only works with Windows XP without actually installing Windows XP on your computer – especially important considering many new laptops and other hardware may not fully support Windows XP.


• Run software designed for another operating systems: Mac and Linux users can run Windows in a virtual machine to run Windows software on their computers without the compatibility headaches of Wine and Crossover. Unfortunately, games can be a problem – virtual machine programs introduce overhead and no virtual machine application will allow you to run the latest 3D games in a virtual machine. Some 3D effects are supported, but 3D graphics are the least well supported thing you can do in a virtual machine.


• Test software on multiple platforms: If you need to test whether an application works on multiple operating systems – or just different versions of Windows – you can install each in a virtual machine instead of keeping separate computers around for each.


• Consolidate servers: For businesses running multiple servers, existing servers can be placed into virtual machines and run on a single computer. Each virtual machine is an isolated container, so this doesn’t introduce the security headaches involved with running different servers on the same operating system. The virtual machines can also be moved between physical servers.

Recommended Virtual Machine Software

VirtualBox is a great, open-source application that runs on Windows, Mac OS X, and Linux. One of the best things about VirtualBox is that there’s no commercial version – you get all the features for free, including advanced features like “snapshots,” which allow you to take a snapshot of a virtual machine’s state and revert to that state in the future – a great feature for testing.

VMware Player is another high-quality virtual machine program for Windows and Linux. VMwarePlayer is the free counterpart to VMware Workstation, a commercial application, so you don’t get all the advanced features you would with VirtualBox. However, both VirtualBox and VMware Player are solid programs that offer the basic features – creating and running virtual machines – for free. If one of them doesn’t work quite right, try the other.



To install an operating system in a virtual machine, you’ll need the operating system’s installer disc – perhaps a Windows installation disc you have lying around. You can also use an ISO image file – Linux distributions usually provide downloadable ISO files you can use. Virtual machine programs offer easy-to-use wizards that walk you through the process of creating a virtual machine and installing a guest operating system.

You can also take a shortcut and download pre-created virtual machines, where a person has already installed the operating system in a virtual machine – all you have to do is load the virtual machine in your virtual machine program and start it up. For a variety of free, already created virtual machine images, check out the VirtualBoxes website.