Dual-boot, no; virtualization, yes

Over at ZDNet, I’ve got some initial reactions to the announcement that Apple has released a utility called Boot Camp, which lets Intel-based Macs run Windows XP. 

I’m not a big fan of dual-booting, which represents a crude solution to compatibility problems. If you own a Mac, you bought it because you want to use your Mac applications. It’s an enormous hassle to shut everything down and boot into an alien operating system to perform a task that can’t be accomplished in the native environment. And while you’re running Windows on your Mac, you’ve lost all access to your familiar Mac desktop and programs. I’m also skeptical that drivers written for Windows XP will work seamlessly on this unfamiliar hardware platform. When you add it all up, this is a feature that diehard enthusiasts might experiment with, but it won’t be particularly useful in the real world.

[Read more: Apple’s Boot Camp is just the start.]

Among Windows geeks, dual-booting is a Very Big Deal. On one private forum I belong to, I recently got into a heated argument with another member, who was miffed that the latest beta builds of Windows Vista make it difficult to change the labels on the boot menu. (Short version: You have to master the syntax of the Bcdedit command line tool.) He had four separate installations of Windows on a single PC. For an average Windows user, that’s probably three too many.

In my opinion, there are really only two valid reasons to set up multiple versions of Windows on a single PC:

1. You’re unable to get into your main OS. If a botched hardware install or a system configuration problem locks you out of your normal Windows installation, setting up a clean copy of Windows (ideally on a separate partition) is an essential troubleshooting step. By starting up in the new, clean copy of Windows, you can either fix the original, broken installation or at least get access to your data.
2. You’re evaluating whether to install a new service pack or upgrade to a new release of Windows. The only sure way you can find out whether your existing hardware and critical applications will work properly is to install them on your hardware. A clean install (again, on a separate partition) lets you test everything without undue risk. You can even clone the existing partition (using Ghost or a similar tool) to test under absolutely identical conditions. After you finish your testing, you decide whether to upgrade or not and blow away the test installation.

So, what if you’re evaluating Windows Vista and you find that you have one or more applications that don’t work properly under the new OS? You could set your system up to dual-boot, but that means every time you want to use that one program you have to shut down everything you’re doing, boot into the other installation, do your work, shut down again, and restart to your regular Windows installation. Ugh.

A much, much, much better solution is to use software that lets you create virtual machines (VMs).

The concept of virtualization is hard to explain, but in essence, what it does is to allow you to use a single physical machine to create one or more environments that look and act just like they were separate physical boxes. The virtualization software is a regular Windows program (you can also find virtualization software for various Linux distributions). When you run the program, you get to define a virtual machine by telling the system how much disk space and RAM to set aside, what kind of network access you want to set up, and so on. You then “boot” the virtual machine using a bootable CD or DVD (or an ISO image file) and install the operating system in the VM. When you’re done, you can go to the window containing the VM and do anything you would do on a physical machine. With a keystroke combination, you can zoom the window to full screen and use the VM as if you had dual-booted. The difference? With another keystroke, you can go right back to your regular OS. No waiting around for your system to shut down and restart, and the Windows Clipboard works between the two environments.

The VM concept has some limitations. Performance is always an issue – VMs almost always run more slowly than physical hardware. In addition, all of the hardware is virtual. That’s an especially important limitation for display adapters. Your copy of Windows running in a VM won’t be able to access your super-fast video adapter, which means that games will run slowly and whizzy effects like Aero Glass won’t work properly. If you want to use Media Center features that depend on hardware such as TV tuners, you’ll probably be out of luck as well. But if you just want to run a program that has compatibility issues on your main OS, a VM is an ideal solution.

I’ve been a very happy VMWare user for some time now. As a technology writer, it’s an indispensable way to test operating systems and software without having to constantly tear apart and rebuild physical machines. I tried using Microsoft’s Virtual PC 2004, but was dissatisfied with its performance and have continued to stick with VMWare.

As I point out in my ZDNet column, Microsoft might actually welcome a virtualization solution that runs on Apple’s Intel-based hardware. Unlike Apple, Microsoft isn’t in the computer hardware business. If someone, anyone, comes up with a virtualization program that allows Windows to run in a virtual machine on an Intel-based Mac, Microsoft gets to sell another copy of Windows and another copy of Office. Think they’re going to complain?