Desktop Linux has floundered for three main reasons: too few applications, limited desktop hardware compatibility, and too few tools (not to mention skilled people) to manage a boatload of Linux desktop systems.

Desktop virtualisation, on the other hand, has had trouble getting off the ground because the value proposition falls just short of compelling. Sure, over the long haul, the benefits of centralised administration outweigh the investments you must make in server hardware, network bandwidth, and the transition to thin clients. But when you throw in the cost of VMware plus one Windows and Microsoft Office license per user, you may have trouble finding the "R" in "ROI."

So what happens if you put desktop Linux and desktop virtualisation together? If it were an all-open-source solution, the cost equation wouldn't even be in the same ballpark.

As InfoWorld executive editor Galen Gruman wrote last year, desktop Linux - in particular, Ubuntu - has come a long way in usability. And last April's release of Ubuntu 10.04 further improved the look and feel with the new, more polished Light interface. As for applications, there's OpenOffice, of course, but also version 3 of Lotus Symphony, which is IBM's most serious attempt yet at a free-as-in-beer alternative to Microsoft Office.

As for open source virtualisation, to take one example, Red Hat updated its Enterprise Virtualisation offering to include support for desktop virtualisation last March. I hasten to add that we have not tested this package or KVM (kernel-based virtual machine), the open source hypervisor on which it is based, though the InfoWorld Test Center plans to do so this summer. I'm not making endorsements. What I'm just saying is that all the pieces are available for you to assemble.

What might happen when you put those pieces together? Well, in addition to vastly lower cost than a Microsoft-based solution, if you use thin clients, then very obviously all potential Linux compatibility problems with desktop hardware evaporate. You also pretty much eliminate all endpoint security vulnerabilities. I'm not naïve about the time and effort that might be required to get such a bleeding-edge VDI solution up and running, nor do I want to imagine what desktop video and audio problems might ensue. But I bet some sufficiently zealous Linux admins could get it all to work.

Of course, no office that depended on Windows desktop applications beyond productivity software would consider such a solution. Plus, there will always be file compatibility problems -documents with special formatting created on Microsoft Office apps may not display or print exactly as they should using Office alternatives and vice versa. (And of course, there's the biggest showstopper of all, when users give you a look that says: "What is this?!")

But as a generic solution for generic office needs, the cost seems positively irresistible compared to the license-heavy Microsoft/VMware version of desktop virtualisation. In fact, if I were starting a small business, I'd consider that or a cloud-based solution like Google Docs or Zoho before I'd seriously contemplate paying $400 or $500 per user for Windows and Office, whether or not all that Microsoft stuff was wrapped into a desktop virtualisation solution.

Even at the corporate level, a fundamental shift may be occurring. Last month I spoke about the impact of open source on IBM customers with Bob Picciano, general manager of worldwide software sales. He cut right to the chase: "If you're asking me whether Microsoft is a lot less relevant now, the answer is absolutely yes."

So if you're already bound and determined to escape Microsoft's clutches, and the benefits of server-based computing sound attractive, it's worth considering. As isolated solutions, desktop Linux and desktop virtualisation have major shortcomings; together they have the potential to be a stronger Microsoft alternative. And an open source desktop virtualisation solution might be better than handing the family jewels to Google Apps. After all, before long, Google may be every bit as big as Microsoft.