When is a desktop PC not a desktop PC? When it's running virtually on an Apple computer. Or loaded with a server's worth of database and applications to create an environment for software testing. Or sitting in someone's pocket, stored entirely on a USB flash drive.

Virtualization has been one of the hottest new technologies of the past few years, and it's easy to see why. In large companies' data centers, software that creates virtual "servers" has replaced actual, physical servers, allowing those companies to better protect their data. Fewer physical servers also mean less electricity and greener IT. But virtualization has its uses for small businesses too -- even those that don't have a single server of their own.

Detaching software from hardware

Virtual personal computers can be difficult to conceptualize because as users we're accustomed to thinking of the hardware and the operating system as one unit. We say "PC," meaning a computer that runs a Windows operating system, regardless of whether it was made by Dell or IBM or Alienware. But virtualization can completely separate the hardware from the code, making a personal computer desktop into nothing more than a file. That file can be stored on a central server or a disk and loaded onto any other machine to recreate the desktop computer exactly as if you had carried the whole thing with you.

For executives and sales people at Elemental Security, an automated security and risk management platform, virtualization means the difference between shipping equipment ahead of time to set up a demo or bringing it with them on a USB drive. "Our platform is pretty complex. It requires an Oracle database, an Apache Tomcat Java environment and a lot of agents," explains CEO Marius Bratan. "We used to use several machines and put several appliances together. It was huge preparation work."

These days, Elemental Security representatives arrive with a virtual version of their environment, created with the virtualization app MokaFive and loaded on a four-gigabyte USB drive. They plug it in to one of the customer's computers or a laptop of their own, and the demo is ready to go. What's more, unlike the complicated appliance setup they used before, the virtual environment can easily be copied onto other laptops or USB drives. Reps can even leave the drives with potential customers to give them time to explore the software's features -- something that would have been impractical and too costly with larger appliances.

For love of Macs

Desktop virtualization software VMware Fusion also allows users to easily combine Mac and Windows environments without having to reboot their machines. "I love Outlook and some of the Windows applications, and I love some applications that only run on Macs," says Ziv Gillat, co-founder and vice president of business development for Eye-Fi, a device which automatically downloads images wirelessly from digital cameras. "This lets me have the best of both worlds."

Virtualization is also invaluable for testing Eye-Fi in different environments, he adds. "Our company is mostly running on Macs for various reasons," he says. "So if we want to test on several Windows operating systems, we load Fusion on a Unix machine and run Vista and XP on that."

Running a Mac and Windows computer combined requires extra memory, adds Timothy Childes, chief chocolate officer of chocolate maker TCHO. The company is a Mac shop but uses Fusion to run software, such as UPS WorldShip that only works in Windows. "Make sure your machines are maxed out on RAM," he says. "A Mac typically comes with one gigabyte. You want at least two, ideally three or four."

Simplifying laptop management

Virtualization has many uses even for companies that don't use multiple operating systems, says MokaFive CTO John Whaley. For one thing, it can vastly simplify managing your company's laptops. "If you give someone a laptop, there are all the headaches of dealing with that laptop," he says. If it becomes infected with malware or needs an update, your company's IT staff will need to do that. A virtual PC can be automatically updated or have new programs installed via the Internet, and it can easily be reset to its original state if it becomes corrupted or infected.

And, virtualization can help keep your data private, he says. "If someone loses a device or leaves the company, the central management console can kill that user," he explains. The next time that virtual desktop connects to the Internet, it will automatically check in with the server, download a "poison pill," and self-destruct.

"Managing desktops and laptops is a huge problem," Whaley says. With virtualization, though, you can manage their entire life cycle more easily, from setting them up, updating them, keeping them running smoothly -- to terminating them when the time comes.

SIDEBAR: Desktop Virtualization Options

Here are some of today's desktop virtualization solutions for small and mid-sized businesses:

  • Citrix XenDesktop provisions virtual desktops from a central server to users both on-site and far away.
  • MokaFive allows you to create a virtual desktop PC that, unlike XenDesktop and VDI, will work even when users aren't connected to the network.
  • VMware VDI (for Virtual Desktop Interface) is a server-based solution that provides virtual PCs from a central console.
  • VMware Fusion, specifically for Apple computers, allows Macs and Unix machines to run virtual Windows desktops.