Windows Vista might suffer another delay in its launch date, analyst firm Gartner has warned in a new research note. 

The note predicted that the forthcoming operating system will not ship until the second quarter of 2007, whereas Microsoft is currently promising to have it ready by January. 

"Do not tie your future too close to Microsoft's expected release dates for Windows," a group of four analysts wrote in the note that has been made available to Gartner clients.

"Microsoft cannot accurately predict release dates more than a few months out, and organisations that are too reliant on Microsoft making shipment dates are leaving themselves open to excessive risk."

A Microsoft spokesman told vnunet.com that Microsoft disagrees with the analyst firm. "We respectfully disagree with Gartner's views around the timing of the final delivery of Windows Vista," he said.

"We remain on track to deliver Windows Vista Beta 2 in the second quarter and to deliver the final product to volume licence customers in November 2006 and to other businesses and consumers in January 2007."

Windows Vista is currently at the Beta 1 stage, targeting enterprise IT users and developers. Microsoft plans to release a second beta in by June, which will be available to a broader set of testers.

Gartner said in its research note that Microsoft is likely to need nine to 12 months after Beta 2 ships before it can release the final product. Microsoft's current schedule allows for only five months of testing.

"We believe that more time is required between a stable, feature-complete Beta 2 and release to manufacturing to accommodate the issues expected during broad testing and allow for at least two release candidates," the Gartner researchers wrote.

Microsoft took 18 months with Windows 2000 from the Beta 2 release to the final product, Gartner pointed out. Windows XP took only five months, but was a relatively minor release.

Gartner projected the long release cycle based on Vista's complexity and the need for enterprises to test internally developed applications.

The analyst also warned that Windows Vista Beta 2 testing is likely to raise many new problems because it will expose the software to new applications and user scenarios.