I'm not usually a great believer in analysts' predictions, but I might make an exception for Gartner's recent forecast for PC virtualisation technology. Hidden among the buzzwords and the obligatory references to total cost of ownership, there was a good deal of sense in what the firm was saying.

Gartner was talking about the use of virtual machines on desktop PCs. Virtualisation has been around for ages in mainframes and high-end servers. Many IBM machines can run a number of different operating systems in separate hardware partitions without even breaking into a sweat. Each operating system is allocated its own virtual processor(s), storage and I/O, and is basically conned into believing that it is in sole charge of the system.

For desktop PCs, applications such as VMware and Virtual PC let you do a similar thing - but in a more limited way. There's less powerful hardware to be shared, for starters, and there's a significant software overhead, as they have to run on top of the host version of Windows.

I now use a virtual machine, and for the exact reasons Gartner talks about. In my last column, I moaned about problems we'd had upgrading applications, only to find they didn't work. So I identified the stable combination of operating system (OS) and application software, then installed this onto a virtual PC. It's easier and cheaper than buying a new PC for the job, and it's pretty well isolated from any changes we make to the underlying OS or hardware.

Gartner has realised this is a neat way of solving the old problem of locking down vital desktop applications. Simply create your stable, secure environment and load it onto a virtual machine running on every user's desktop. The users can't fiddle with it, but can still install their favourite screensaver onto the host OS.

The software overhead for virtualisation can be as much as 15 to 20 percent, but hardware technologies are coming in the next couple of years that will make virtual machines more attractive. Intel's Vanderpool project is designed to put technology into PC chips to offer hardware support for virtualisation, reducing much of the software overhead. I think it's a great idea; the only remaining question is, what host OS do you use?

This is where things get interesting. There are currently only two real commercial contenders for virtualisation tools: EMC's VMware, and Microsoft's Virtual PC. Microsoft's offering currently runs only on Windows PCs, while VMware can also run on Linux. Unless Microsoft radically changes its licensing policy, the only cost-effective way of virtualising your Windows clients will involve Linux as the host OS. Or perhaps Microsoft will incorporate the technology as a standard feature of Windows. Now that would explain Gartner's bullishness, but it couldn't possibly happen. Could it?

Well, the open-source Xen virtual machine monitor project at the University of Cambridge - see the URL below - has already produced an experimental version of Windows XP with built-in virtual machine technology. The work is supported by the UK government, Intel, HP and Microsoft. Could this be a taste of things to come?