So, you're studying for the CompTIA A+ Certification exams and you realize that
- you have only one computer.
- you need to understand how Windows XP and Windows Vista differ in terms of management tools, command-line utilities, and user interfaces.
- you don't want to keep rebooting your computer to switch between operating systems.
- you don't want to buy a new computer just to run a different operating system.
What's the answer? Virtualization.
In this article, you'll learn how virtualization enables you to have two or more operating systems running at the same time on a single computer so you can compare how they work and practice using them.
What Is Virtualization?
Virtualization refers to the creation and setup of logically separate "computer within a computer" environments on the same physical hardware. With virtualization, a single computer can run two or more operating systems at the same time.
By using virtualization, you can run your preferred operating system as well as one or more guest operating systems in separate windows.
In the example shown in Figure 1, Windows XP is running inside of Windows 7 using Windows 7's XP Mode.
Figure 1 Windows 7's Professional and Ultimate editions enable you to run a free virtualized installation of Windows XP known as XP Mode.
There are several methods that can be used for creating virtualization environments in a computer. The most common include the following:
- Using a host operating system to run guest operating systems through virtualizing software. This is the method used by Microsoft's Virtual PC 2007 and Windows Virtual PC as well as Sun Microsystems' VirtualBox and VMware's VMware Workstation, VMware Server, and VMWare Player.
- Running a hypervisor virtualizing program as a host to run guest operating systems. This is the method used by Microsoft's Hyper-V, VMware's ESX Server, Citrix's XenServer, and others.
The host operating system + virtualizing program + guest operating system method is the best choice for experimenting with different operating systems and for comparing different operating systems.
By contrast, the second approach is designed to enable a single mission-critical computer, typically a server, to replace multiple physical servers with a single physical server running multiple virtual machines that might be running the same operating system but are conFigured to perform different tasks.
You can see diagrams of these and other approaches here.