Microsoft has started preparing preparing its partners for the eventual arrival of Windows Vista SP1 (Service Pack 1).

Microsoft officials have not yet released the schedule and details for a service pack update for Microsoft's Windows Vista operating system. But Microsoft has now started openly referencing the upcoming Vista SP1 release in documentation on its website.

Industry experts have long predicted the arrival of a Windows Vista SP1 release. Some observers have been looking for Service Pack 1 even since before the launch of the OS in late 2006. But Microsoft remains steadfastedly tight-lipped on what its plans for the SP1 update might be.

Windows Vista - the definitive review

On 7 June, Microsoft posted documentation for a Windows Automated Installation Kit on its Download Center portal that applies to a product dubbed Windows Vista SP1 Beta 3.

The Windows AIK (Windows Automated Installation Kit) is designed to help OEMs (original equipment manufacturers), system builders and corporate IT departments deploy the OS on to new hardware, Microsoft said.

As part of the announcement, Microsoft posted a document which indicates that Windows Vista SP1 has been under development since at least February 2007, the date amended to the file which provides an informational overview of the download.

Some German researchers were also recently able to sneak a screenshot that references Vista SP1 from a presentation at the WinHEC (Windows Hardware Engineering Conference) in Los Angeles in mid-May.

Microsoft officials didn't immediately respond to calls seeking comment on the details of Vista SP1.

When SP2 for Microsoft Windows XP first arrived in August 2004 it set off a wave of discontent as many businesses had problems installing the update.