The promise of desktop virtualization technology is to centralize applications at the datacenter to make them easier to manage and provision -- stretching hardware resources and keeping nagging software conflicts to a minimum in the bargain. In some cases, the same technology helps accomplish all three, bringing greater control and flexibility to IT without users mourning the loss of "their" beloved desktops.

At first blush, desktop virtualization sounds a lot like terminal services such as those provided by Citrix Systems, where servers run the applications and give users remote access. All the user's terminal or PC does is present the updated screen display and permit input via keyboard and mouse.

Desktop virtualization, on the other hand, is a new way of delivering the individual PC environment that white-collar workers demand and love. In essence, servers host an entire desktop environment specific to each user.

The early versions of desktop virtualization were blade servers such as those offered by ClearCube Technology and IBM that simply moved the processing guts of a PC to the datacenter and left the input and display at the user's desk. But the latest versions use the PC at the user's desk for much of the processing. Dubbed "desktop streaming," this approach retains the benefits of central management without throwing away the desktop's power. The needed code is streamed to disk and memory cache for just that session, ensuring that there's nothing for the user to mess up or alter.

A few providers go beyond desktop streaming to application streaming, where IT can send out the runtime cache for individual apps as needed. This reduces the number of unique user images to maintain and provides better insight into which application licenses are really needed.