Microsoft will release the first near-final version of its Windows Server 2008 operating system as early as next week.

"We expect the release candidate next week," said Mike Neil, Microsoft's general manager of virtualisation, during a speech at the Intel Developer Forum in San Francisco.

The release candidate will include a test version of software code-named Viridian and formally called Windows Server virtualisation. This "hypervisor" allows multiple operating systems to run simultaneously, a useful technology in improving server efficiency and eventually leading toward more flexible data centre operations.

Neil showed a server running virtual machines on Viridian -- one the bare-bones "reduced-footprint" version of Windows Server 2008 and another Novell's Suse Linux Enterprise Server. The software can take advantage of the horsepower of a four-processor Xeon system, Neil said.

Microsoft hasn't had a smooth time delivering either software to the market. In May, Microsoft stripped out several significant Viridian components from the first version of the technology, and in August, it delayed Windows Server 2008's release to manufacturers from the fourth quarter of 2007 to the first quarter of 2008.

Viridian is scheduled to ship in final form within 180 days of the final version of Windows Server 2008.