Ever since Vista was released, there has been discussion of when Microsoft would deliver SP1, and whether or not that delivery would be a significant milestone in the OS's development. Microsoft has downplayed the importance of Vista service packs for months, arguing that Vista is "high quality right out of the gate," but in the eyes of many businesses and consumers, the release of an operating system's first service pack is the point at which the product begins to shift from "early release" to "mature product."
Microsoft has released Vista's SP1 to a group of select beta testers, but a Windows Update spoof has been discovered that allows any user to unofficially "join" that group. CyberNet News reports (via Ghacks) that a simple registry change will display Windows Vista SP1 as an available update ready for download. Installation of the beta will place an "Evaluation" watermark on the screen, but Ghacks has information on removing this as well. We don't recommend doing this on your main system—the service pack is still in beta, after all—but it's potentially useful as an early preview tool for anyone who can load Vista on a secondary system or test rig.
News source: Ars.Technica