Major update: Microsoft has finalized Windows Vista Service Pack 1 (SP1) and released it to manufacturing. This FAQ has been updated to reflect the final release, and Microsoft's schedule for getting this code into the hands of its users.

While most Windows service packs are hardly worth discussing, Windows Vista Service Pack 1 (SP1) has been steeped in mystery almost since before Vista itself was completed. With Vista, Microsoft has engineered a new update deployment technology that allows administrators and power users to "slipstream" service packs and other fixes into new Vista installations in a manner that is much simpler than with previous Windows versions. But the real issue with SP1 is in how Microsoft has mishandled the dissemination of information about this release. For this reason, and because there are so many silly rumors floating around, I've created a FAQ for Vista SP1 that will be updated as new information is released. If it's not in this FAQ, it's just speculation.

Q: What is Windows Vista Service Pack 1 (SP1)?

A: Windows Vista SP1 is the first major update to Windows Vista, a collection of bug fixes, minor functional changes, and other additions to Microsoft's latest operating system. As is the case with Vista, however, the feature set for SP1 has changed dramatically over time. Originally, Microsoft hoped to ship a Media Center update with SP1 but this update will no longer be included in SP1. Indeed, from an end user point of view, there won't be any major functional changes added to Vista with SP1.

Q: Why all the secrecy?

A: During a Microsoft briefing in 2006, I was told that the company planned to ship SP1 alongside Windows Server 2008, which is exactly what happened. However, in the interim, Microsoft CEO Steve Ballmer twice publicly disavowed any knowledge that the company had even considered releasing such an update. The first time he said this was at the Windows Vista business launch in November 2006, and I was in the audience at the time. My guess is that Ballmer didn't want to discuss SP1 then because the company's corporate customers typically wait for the first service pack release of an OS before upgrading. Microsoft was hoping that with Vista, companies would upgrade on the initial release and not wait for a service pack. Now we know that Microsoft's corporate customers are proceeding as they always do, so Microsoft begrudgingly begun discussing SP1.

In late August 2007, Microsoft finally came clean about SP1 by officially announcing the update and explaining its feature set, such as it is. That release is now complete. However, for over a week after the finalization of SP1, Microsoft continued to be secretive about how it would ship this release to customers. That information, finally, is now public as well.

Q: What features are included in Vista SP1?

A: The following end-user features are included in Windows Vista Service Pack 1:

1. A collection of previously-released and new security fixes, bug fixes, and other minor updates.

2. An update to the Windows kernel to bring the Vista kernel (version 6.0) up to date with the version in Windows Server 2008 (version 6.1).

3. A change to the Kernel Patch Protection ("PatchGuard") feature in the Vista kernel that prevents security companies like McAfee and Symantec from integrating as tightly with the OS as they could in previous Windows versions. This will include a set of APIs aimed at helping developers write code that interacts with this security feature.

4. A change to Vista's Instant Search feature that will allow third party desktop search product makers to more closely integrate their products with Windows Vista. In the initial shipping version of Vista, the Instant Search indexer still runs at full speed even if a third party product is installed, reducing overall system performance.

5. A change to Windows Genuine Advantage (WGA) that will remove the Reduced Functionality Mode (RFM) and Non-Genuine State (NGS) mode for Vista installs in expired non-activated and non-genuine states. See New WGA Behavior in Windows Vista Service Pack 1 for more information about this change.

And folks, that's about it. For a more complete rundown of SP1's features, please read my showcase, Windows Vista Service Pack 1 Revealed.

Q: Surely there's more to Vista SP1?

Actually, yes. In addition to the obvious functional changes listed above, Vista SP1 includes a number of low-level changes that improve the overall Vista experience in a number of ways. These include:

Device compatibility is up dramatically, from a bit over 40,000 compatible devices to just under 80,000 devices today with SP1. The number of logoed devices--devices that are certified by Microsoft to work properly with Vista--is also up dramatically, from about 2000 at launch to over 17,000 today. Microsoft director Chris Flores pointed out to me that the improvements to Vista's drivers aren't limited to sheer numbers, either: Improvements to video, audio, and other drivers have actually improved the battery life on laptops from several major PC makers by an average of 7 percent.

Application compatibility, too, improves significantly with SP1. While this area includes consumer-oriented applications, incompatible enterprise applications were the big deployment blockers over the past year. In the past year, Microsoft and its partners have remediated over 150 enterprise application blockers: These are applications that previously prevented one or more corporations from upgrading to Vista.

Reliability is up in Vista SP1, too, Microsoft says. Flores described the company's telemetry data, which allows it to analyze various system disruptions in Vista, including such things as non-responding applications, application hangs and crashes, and system crashes. Compared to the release version of Vista, SP1 more than doubled the mean number of hours between disruptions, from about 17 hours to about 34 hours.

File copy improvements. One of the biggest complaints users have had with Windows Vista concerns file copy operations, both locally on a single PC and over networks. Microsoft isolated the cause of these and provides the fixes in SP1. A number of areas are affected, including the performance of file copy operations and system responsiveness during these operations. According to the latest data, file copy operations are 44 to 71 percent faster with SP1 than they were under the original version of Vista. Microsoft has also improved the speed at which Vista resumes from Sleep or Hibernation in SP1.

Security is another oft-discussed aspect of Vista, and Microsoft points to a number of recent studies of the system compared to rival OSes and its own predecessor, Windows XP. "Users are far less likely to be infected with malware or spyware on Vista," Flores told me. "We're really happy how Vista stacks up, security-wise." One interesting item that came up during the development of SP1: The highly-criticized User Account Control (UAC) feature in Vista only needed to be changed in two small ways for SP1 because Microsoft's data shows that the majority of consumer sessions don't require any UAC prompts at all after the first 30 days of use.

Q: When will Microsoft release Vista SP1?

A: This is where things get confusing.

Microsoft announced the RTM, or finalization, of Windows Vista SP1 on February 4, 2008. However, it is releasing the update in a staged fashion. How and when you can get this update will depend on a number of factors. Here's how it breaks down.

Upgraders. Those wishing to upgrade an existing Windows Vista-based PC to SP1 will be able to do so in mid-March 2008 or in mid-April 2008, depending on their hardware configuration. Apparently, Microsoft discovered a small number of device driver issues late in SP1's development, so it needs some time to fix those before it can ship SP1 to systems with that particular hardware installed. If you enable Windows Update to automatically download updates and do not have any of the affected hardware installed, you'll be getting SP1 in mid-March. Otherwise, it will be mid-April. And no, Microsoft is not announcing which hardware is the problem, sorry.

Standalone downloads. The standalone versions of the SP1 downloader will be made available in mid-March.

Preinstalled on new PCs. New PCs with Vista and Service Pack 1 will appear on store shelves "in the coming months." PC makers began receiving the SP1 code on February 4, 2008, but it will likely take a few months before new PCs based on that code hit the market.

Retail copies of Windows Vista with Service Pack 1. If you're hoping to buy a retail, boxed copy of Windows Vista with SP1 preinstalled, those versions of the system will also replace the initial Vista release on store shelves "in the coming months."

Enterprise customers. Corporate users who participate in Microsoft's volume licensing programs will receive DVDs with Vista and SP1 integrated in the coming weeks. Microsoft says they are manufacturing these disks immediately.

International users. On February 4, 2008, Microsoft RTM'd only the English, French, Spanish, German and Japanese language versions of the update. The remaining languages Microsoft supports will be released to manufacturing in April and ship worldwide after that.

Q: Why the convoluted release schedule?

A: Microsoft says that it identified some hardware incompatibilities late in the testing phase for SP1 and wants to correct those issues--reportedly related largely to networking hardware--before shipping SP1 to customers. The company expects to complete this work between mid-March and mid-April. So customers without the affected hardware will get SP1 first.

Q: Any word on when Microsoft will ship the much-need "Fiji" Media Center update?

A: No, when I last spoke with the Media Center team, I was told that Microsoft shipped a Media Center update every year around the holiday season and they would try to keep doing that. At the time, SP1 was expected by late 2007, so the delivery schedule made sense. Right now, it's unclear if the Media Center update will ship out of band by itself to Vista users this year or as part of a set of related updates (like "XP Reloaded" from 2005) later on. What is clear is that it will not ship as part of SP1.

Q: Where can I learn more about Vista SP1?

A: My Windows Vista Service Pack 1 Revealed showcase includes a detailed rundown of everything that's Microsoft will deliver in Vista SP1. Also, stayed tuned to my Vista Activity Center for the latest information: My review of Windows Vista Service Pack 1 will be available soon.