CIO Roxanne Reynolds-Lair of The Fashion Institute of Design and Merchandising wanted to bring both Macs and Windows to her college's students, administrative employees and teachers. She bought a MacBook Pro and tested new-fangled desktop virtualization software that allows her to run both Windows and OS X on a single machine.Then she looked at software licensing, which is struggling to catch up to the emerging virtual desktop world. Shaking her head, Reynolds-Lair shelved the desktop virtualization project. "It doesn't make sense," she says. "It's really not ready yet."[ Learn the basics of desktop virtualization. | Check out desktop virtualization's devilish details. ]Desktop virtualization promises to put an end to the platform wars. The technology lets a person toggle between different operating systems, which can run locally on the same computer or hosted on a server miles away and accessed over the Internet. Yet glitches and inconsistencies still need to be worked out. Hidden infrastructure and support costs also creep into the equation.But the biggest hurdle to desktop virtualization, either the hosted or local variety, is untangling software licensing agreements that traditionally tie a single operating system or application to a single computer. To wit, software vendors haven't figured out how to adapt their businesses to virtual desktops.In order to make local desktop virtualization work, for instance, Reynolds-Lair would've had to buy two licenses\u2014one for the Mac, one for the PC\u2014for Adobe Photoshop, as well as two licenses for Adobe Illustrator, for every computer in The Fashion Institute's labs."Why charge twice for the same piece of software just because you're running two operating systems?" she says. "We can't tell our students to only use Photoshop on the Mac side and Illustrator on the PC side. That would be absurd."Microsoft gets serious about licensing in virtual desktop scenariosSoftware licensing has stymied desktop virtualization adoption on two fronts: OS licensing and third-party software licensing.With the OS, Microsoft handcuffed many organizations that attempted to legally license Windows in a desktop virtualization environment, says Forrester Research analyst Natalie Lambert. In January, though, "Microsoft opened up licensing to deal with desktop virtualization scenarios," she adds.Today, Windows licensing for local desktop virtualization is fairly straightforward. Companies can buy Microsoft's Software Assurance for a 29 percent premium on their current Windows license costs, entitling them to run up to four virtual machines on top of a Windows host OS on a single PC.Windows licensing in a hosted environment, though, is a little more tricky. Microsoft's Vista Enterprise Centralized Desktop license allows companies to run Windows on a server. But costs vary depending on the kind of device used to connect to the virtual Windows desktop, such as company-owned computers or non-company-owned ones."Microsoft has made scenarios for other devices, however, they're not going to let you get off that easily," Lambert says. "If you're an employee who has a Mac at home and wants to access the [Windows] virtual machine, you're allowed to do that as long as there's a Windows machine at home as well. Microsoft is saying there's scenarios we'll make possible as long as you've purchased a Windows license somewhere."Software vendors lag behind virtual desktop movementThird-party software vendors also throw a monkey wrench into the desktop virtualization machine. Reynolds-Lair wants to see software licenses charged based on a computer's serial number rather than on the operating system. This way a single Adobe Illustrator license would be charged for Windows and Mac OS X running on a single machine."As the dual operating system gets perfected and software licensing issues get worked out, Macs will take a larger market share," Reynolds-Lair says. "We just need it to work seamlessly first."Many CIOs, though, don't see a problem with application tools. That's because they wouldn't run the same application in both Windows and OS X. The reason many companies roll out desktop virtualization is because an application isn't available on both platforms. Still, other applications such as anti-virus software are charged by the OS and thus cost twice as much in a desktop virtualization setup.But change is in the wind. "Vendors are hearing from their customers that they have to fix it," says Forrester's Lambert. "It's going to be another six months to a year."