Hardware & Infrastructure
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3/30/2004
05:23 PM
Fred Langa
Fred Langa
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Langa Letter: Virtual Excellence: Microsoft's 'Virtual PC' Is Too Good Not To Check Out

In this introduction to the technology, Fred Langa says Microsoft Virtual PC provides a viable alternative to dual booting and should be a solid choice for software testing, evaluation, and support.

Late last year, Microsoft quietly rolled out its entry into the "virtual PC" arena--Microsoft Virtual PC 2004--and delivered its offering at about half the price of competing commercial products. What's more, Microsoft even offers a 100% free, 45-day trial of the software.

I've recently experimented with the software and think it deserves a close look by anyone seeking an alternative to dual-booting (say, to run Linux on a Windows PC); as well as by those involved in the traditional uses of virtual PCs, including software testing, evaluation, and support.

What follows isn't a formal software review, but rather an introduction to a technology you may not be familiar with--but that just might change the way you use your PC. While we'll focus on Microsoft Virtual PC, the concepts explained here also apply to other virtualization products, some of which we'll discuss later.

What It Is
A virtual PC is a standard desktop computer emulated in software. You can install an operating system, applications, or utilities on a virtual PC and use it the same way you do on a standard PC. The installed software thinks it's running on a normal, physical system, but it's not: Instead, it's running inside a protected memory space on a host system, with special emulation software masquerading as a separate and standalone BIOS, motherboard, hard drive, floppy, CD drive, display adapter, network card, and so on. A virtual PC provides all the normal hardware of a standard PC, created entirely in software.

This concept may seem murky, but it becomes clearer when you see how it's set up and used.

For example, say you install Microsoft Virtual PC 2004 software on your existing PC: It installs just like any other utility onto any PC running XP Pro, Win2000 Pro, or XP Tablet Edition.

When you first run it, the VPC software creates a new empty virtual PC (at this point, mostly just a space in RAM) and a virtual hard drive (at this point, just an empty file). The amount of RAM and hard drive space is fully customizable, although the VPC software will offer reasonable defaults.

When you start the new virtual PC (via a click on a "Console" that controls the VPC operation), a window opens on your current desktop. As the VPC wakes up, the emulated hardware starts to work, and you'll see what looks like--and is--a normal boot process going on inside the window. Outside the VPC window, your original operating system continues to function normally. Your system isn't booting--only the virtualized hardware is.

As the virtual PC hardware wakes up, it discovers the virtual BIOS, virtual drives, and other virtual hardware, and appears to perform a completely normal hardware boot, just as if you'd fired up a factory-fresh, virgin PC with an unformatted and empty hard drive.

Because there's no operating system or other software yet installed on the virtual PC, the hardware boot process ends with a normal prompt to insert a bootable floppy or a setup CD. When you do so, you can either let the new operating system format the virtual drive itself (most modern operating systems are self-installing); or you can manually FDISK, partition and format the virtual drive; and then manually install and set up the operating system of your choice. All this takes place entirely inside the virtual PC, without touching your real setup, and without affecting your real hard drive.

The Microsoft VPC software can run just about any operating system that normally runs on standard Intel- or AMD-class systems: DOS, Windows 95/98/ME/NT/2000/XP, Linux; etc. The VPC software doesn't provide these operating systems, of course, it just provides a means to run them.

When you're done, you'll have your original, normal operating system running--in fact, it's been running all along--with a window open in which a separate operating system is running in safe isolation.

As far as the second operating system is concerned, it's the only operating system on the PC; it's normally prevented from seeing the host operating system, or the host operating system's files. That means the secondary system normally can't affect or crash the host operating system. Whatever happens inside the virtual space stays there.

But even though it's safely isolated, all the normal PC functions are emulated, so the secondary operating system can use the network, access printers, go online, and so on: It's a fully functional PC in essentially every way--but safely isolated inside your main operating system.

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