Windows Tip Sheet

Virtual Computing Rules

It's hip, it's cool, it's virtual computing. Well, it's cool for geeks, anyways.

You know how sometimes you get so used to working with something that you forget how cool it is, and then you're surprised when you meet other people and they haven't heard about it? I bet you have two or three cool tools that you think everybody must know about. My cool tool is Microsoft Virtual PC or, if you prefer, VMWare Workstation.

The whole concept of virtual computing is cool. Virtual PC (and VMWare, for that matter — for the purposes of this discussion, they're identical) runs on your computer and runs other operating systems in a window. Basically, Virtual PC emulates an Intel computer, which you can configure with up to three hard drives, four network adapters, as much memory you want, and so forth. You then install Windows (or Linux, or whatever) on it, just like you would on any other Intel-based computer. So your computer effectively has two operating systems running: The "host" operating system, which in my case is Windows XP Pro, and the "guest" operating system, which in the figure below is Windows 2003 Standard.

Microsoft Virtual PC is my cool tool
With my version of Microsoft Virtual PC, the host runs Windows XP Pro and the guest operating system is Windows 2003 Standard. VMWare also allows Apple Macintosh, Novell, and Unix or Linux to run on the same box in virtual PCs. (Click image to view larger version.)

But the fun doesn't end there. Provided you have enough RAM on you host machine, you can run multiple guest operating systems at once. The RAM is really key: Suppose you have two guest systems running and that you've allocated 256MB to each. Your physical computer, then, must have 512MB of physical RAM installed, plus extra physical RAM to run your host OS, so about 712MB total, at a minimum.

Perfect For Labs and Pilots
Why is Virtual PC (or VMWare) so cool? Labs and pilots. Imagine being able to pilot an AD migration over and over and over again, running both your NT PDC and your new AD DC on the same physical computer, all safely within a virtual machine window. And I'm serious about the "over and over and over" part, thanks to another cool feature that Virtual PC and VMWare offer: Undo drives.

See, each hard drive hooked up to a virtual computer is really just a file on your host machine (a .VHD file in the case of Virtual PC). When you start a virtual machine, you can have Virtual PC treat that file as read-only; any changes made to the hard drive are written to a separate VHD file called the "undo" drive. In effect, the virtual machine's current hard drive state is the combination of the two VHD drives. When you shut down the virtual machine, you have the option to commit changes, which merges the temporary "undo" drive into the main VHD. Or — and this is the cool part — you can simply discard the "undo" drive, leaving your virtual machine back where you started. This feature allows you to "go back in time" and discard whatever you did to the virtual machine — perfect for a test lab or pilot project!

So what's your cool tool? Something you take for granted and assume everyone has heard of — but maybe they haven't? E-mail me at [email protected] and let me know!

Micro Tip Sheet

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More Resources
Microsoft Virtual PC Web site:

VMWare Web site:

About the Author

Don Jones is a multiple-year recipient of Microsoft’s MVP Award, and is Curriculum Director for IT Pro Content for video training company Pluralsight. Don is also a co-founder and President of, a community dedicated to Microsoft’s Windows PowerShell technology. Don has more than two decades of experience in the IT industry, and specializes in the Microsoft business technology platform. He’s the author of more than 50 technology books, an accomplished IT journalist, and a sought-after speaker and instructor at conferences worldwide. Reach Don on Twitter at @concentratedDon, or on Facebook at

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