Virtualisation software enables you to run multiple operating systems on your Mac at the same time.

Unlike Apple's free Boot Camp solution it doesn't require you to reboot the Mac when you want to switch system. VMware Fusion and Parallels Desktop have battled for supremacy in virtualisation on the Mac, and Sun's VirtualBox is trying to mount a challenge of its own.

However, with Fusion 2, we think VMware has raised the bar, building on its already strong foundations with indispensable new features.

Why Windows?

You might be wondering why anyone would want to run Windows on a Mac, but for the unfortunate minority, Microsoft's operating system clings on, like a particularly determined leech. For example, office workers rely on business software unavailable for Macs and web designers need Internet Explorer for testing websites in. And while Boot Camp provides Leopard users with a dual-boot solution, switching back and forth between Windows and OS X by rebooting your Mac isn't practical if you regularly need to work with software on both systems.

Fusion's ability to run multiple operating systems simultaneously isn't unique, but it's certainly the best implementation we've seen. Purists might argue that performance takes a hit (and they'd be right – our tests indicate that VMware Fusion 2 benchmarks are roughly two-thirds of running Windows via Boot Camp, although Fusion's new ability to utilise multiple CPUs helps things along), but in general use you probably won't notice this, unless you're running games, which isn't a great idea anyway – despite Fusion's improved DirectX 9.0 support, games often run slowly or fail entirely.

Stress-free installation

The application is snappy, responsive and well-behaved, taking up fewer resources than Safari when idling in the background. Or, to put it another way, we actually forgot we had Fusion running in the background – for three whole days. This shows how little impact it has on OS X.

If you've heard or experienced horror stories with Windows, you'll be pleased to know that installations via Fusion 2 are typically a breeze. You can install a guest operating system via a disk, a disk image, or by attaching an existing virtual disk. In all cases, Fusion aims to deal with OS system settings, largely based on your Mac's settings, so the chances are you won't have to fiddle with your new virtual machine prior to booting it.

This thinking extends to Linux systems as well – tests with Ubuntu went very well, with Fusion going so far as to pick up which specific distribution was being installed.

Data migration

Should you already have a PC – virtual or otherwise – Fusion provides tools to help migrate data.

During our tests, VMware Importer, designed to convert Parallels Desktop data, failed miserably, but VMware Converter, a tool for migrating data from a real Windows PC, worked flawlessly, saving us the hassle of reinstalling our Windows applications and data.

Note that VMware provides a step-by-step video tutorial on its website if you need reassurance regarding the steps to take.

Shared data

Configuration-wise, we had little to do during our Windows installs. Our printer was automatically found
(and worked), as were other attached devices. An exception is for shared data, which requires a trip to the Sharing section of the beautifully laid out Settings panel.

Here, you define which folders to share on your Mac, enabling you to drag documents from Finder to guest system applications. This is important, because omitting this step seems to force Fusion to rely on temporary files, which don't work very well.