Microsoft is simplifying its Windows Server System licence to make it easier for customers to run multiple virtual images of Windows on a network.

Part of the company's Microsoft's Dynamic Systems Initiative, the idea is to promote adoption of network virtualisation technology, said the general manager ofinfrastructure server and IT pro marketing, Bob Kelly.

Microsoft will no longer require a customer to pay for inactive or stored virtual images of Windows Server System on a network. Instead, Microsoft will only charge for the virtual images of Windows Server System products actually running on a customer network, a change that will reduce licensing fees.

Windows Server System includes the Windows Server family, Microsoft Operations Manager (MOM), Systems Management Server (SMS) and a host of other server software that runs on Windows.

Virtualisation technology enables multiple images of an OS or other software to run in a virtual machine on a server with only one actual copy of the software deployed. It's become an especially helpful technology as customers increasingly want to consolidate servers, or backup existing systems without investing in a host of new hardware, said Laura DiDio, research fellow with The Yankee Group.

Microsoft will allow customers to have four virtual machines running on top of Windows Server 2003 R2 Enterprise Edition and Windows Server "Longhorn" Datacenter Edition at no extra cost, Kelly said.

Windows Server 2003 R2 is expected to be released before the end of this year, and the Longhorn Datacenter Edition will be available when the Longhorn version of Windows Server ships next year.

With software licensing already a complex maze for customers to navigate, Microsoft's simplication is a wise move. But, as ever, its decision is not purely altruistic. With the expanded virtualisation use rights for future high-end versions of Windows Server, Microsoft also is trying to retain and win more data-centre customers, a market that accounts for only about one percent of Windows revenue and is heavily populated by Linux, DiDio said.