Microsoft on Wednesday finally disclosed the timing and content of Windows Vista Service Pack 1 (SP1) and Windows XP Service Pack 3 (SP3), two eagerly awaited OS updates that were previously shrouded in mystery. The company says that neither update will include any major new end user functionality, especially in the case of Vista SP1, as that OS brings with it a new form of servicing, where updates are released as needed, and not all at once in a service pack.

"Windows Vista SP1 beta will be released in a few weeks to a moderate sized audience," a Microsoft representative told me. "At this time, SP1 will contain changes focused on addressing specific reliability and performance issues, supporting new types of hardware, and adding support for several emerging standards. Microsoft is targeting first quarter of 2008 for Windows Vista SP1."

The Vista SP1 beta will proceed in stages, and the audience for the beta will grow with each stage. Currently, a very small group of testers are evaluating an early version of SP1 code. That group will grow larger in a few weeks, and then a later pre-release of SP1 will be available to a larger group of testers via MSDN and TechNet subscriptions, Microsoft says.

Microsoft would prefer that its business customers especially not wait until Vista SP1 before deploying Vista. As I first reported about quite a while ago, Microsoft plans to ship Vista SP1 and Windows Server 2008 at the same time; the company finally corroborated this information in today's announcement.

As for Windows XP SP3, this release is due in the first half of 2008 and will also be a minor update. "Windows XP SP3 is rollup of previously released updates for Windows XP including security updates, out-of-band releases, and hotfixes," according to a Microsoft representative. "It will also contain a small number of new updates. This should not significantly change the Windows XP experience." Microsoft has yet to reveal what these new updates are.

I'll have more information about Vista SP1 later today in my Windows Vista SP1 FAQ on the SuperSite for Windows.