Microsoft on Thursday released for public evaluation a trial version of its long-awaited Windows Server Longhorn operating system.

Microsoft has made nine versions of the software available as a free download from its Longhorn Web site, ranging from a 32-bit standard edition to a 64-bit data center edition. A special version for servers powered by Intel's 64-bit Itanium processor also is available.

All versions are available in English, German, and Japanese. Beta versions of Longhorn also can be obtained on a DVD shipped through the mail, Microsoft indicated.

Microsoft has said it plans to ship a final version of Longhorn in the second half of this year. It's the company's first major server software release since it unveiled Windows Server 2003.

Among the software's more highly anticipated features are Windows PowerShell, a command line shell with more than 130 management tools and an integrated scripting language, and Internet Information Services 7.0 -- a built-in Web server that brings together numerous online publishing technologies.

Within 180 days of Longhorn's launch, Microsoft plans to release Viridian, software that is a key part of the company's campaign to develop server virtualization products that can compete with those offered by specialists like EMC's VMware unit. Microsoft is designing Viridian so that it can scale across servers running up to 64 processors.

The minimum hardware requirements for running the trial software -- officially known as Windows Server Longhorn Beta 3 -- are a 1-GHz processor, an 8-Gbyte hard drive, and 512 Mbytes of RAM, though Microsoft recommends a 2-GHz processor, a 40-Gbyte hard drive, and 2 Gbytes of RAM.