Microsoft is working hard on the second service pack for Windows Vista, the new SP2 will arrive before Windows 7 and is part of the software giant's campaign to spur Windows Vista sales:
Windows Vista already saw the release of its first service pack in May of this year. The first release was marred by compatibility difficulties, which forced Microsoft to take it offline for a short time. Amid slower than-hoped-for adoption growth, Microsoft launched a reinvigorated push to convince people to adopt Windows Vista, highlighted by its "I'm a PC" commercials.
Reports indicate that Microsoft is hard at work preparing the second generation service packs, to help further this new campaign. It has reportedly delivered a beta of the Vista pack to select hardware and software partners. This is similar to its current distribution method for early builds of Windows 7. Microsoft also posted a placeholder article for Vista SP2 on its Knowledge Base site.
Details on the new packs are scarce, but sources with Microsoft say that the biggest deliverable for the Server version will be the integration of Hyper-V bits with it. Sources also say the reason Microsoft is pushing to release the pack before Windows 7 is to limit confusion about whether to upgrade to Windows 7 or choose the newly more functional Vista.
Few details are known about SP2, but it's rumoured the new service pack may bring some of Windows 7's functionality to Windows Vista. More info at DailyTech.