The platform will be officially launched at an event in Los Angeles on 27 February, Microsoft revealed at its Worldwide Partner Conference in Denver.
The delay is another setback for the software vendor, which has been struggling to get Windows Vista and Office 2007 out of the door in a timely fashion.
The server operating system was formerly known by its 'Longhorn' codename. The launch will coincide with the official unveiling of Visual Studio 2008 and Microsoft SQL Server 2008.
Microsoft tried to put on a brave face about the delays. In a posting on its Windows Server blog, the company claimed that the software will still be "released to manufacturing" this year.
Although this means that server vendors will be able to start testing the code for their systems, end users will not be able to purchase or install the software.
The delay also raises questions about the release schedule of Windows Vista Service Pack 1.
Microsoft has always maintained that the set of patches and updates will be released at the same time as Windows Server 2008, leading most customers to plan for a release by the end of this year.
Many businesses are holding off on installing Windows Vista and Office 2007 until the release of SP1.
If Microsoft persists in launching the two applications at the same time, that would further delay mainstream enterprise adoption of the software.
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