Several popular technology Web sites have posted prerelease updates to Microsoft's Windows Vista operating system, and some are maintaining that the piece parts will become part of the first official service pack for the new OS.

One file, the Vista Performance and Reliability Pack, "resolves a number of individual issues which may be affecting some computers running Windows Vista," according to text from Microsoft that accompanies the software.

Among the pack's promised enhancements: improved performance in returning to the desktop from Vista's Photo and Windows Energy screen savers; resolution of an issue that causes Vista to corrupt some AVI files; and faster restoration of the login screen when resuming from hibernate.

The pack also fixes an issue that may cause incorrect display of Internet Explorer pages.

The second file, the Vista Compatibility and Reliability Pack, also offers a number of fixes. Improved visual appearance of games, better networking reliability, increased printer compatibility, and sharper HD-DVD and Blu-Ray playback are among them.

The fixes were offered over the weekend to participants in Microsoft's beta test program for Windows Server 2008, but quickly leaked onto the Internet.

The broad scope of the patches has led a number of Internet bloggers to speculate that they are a precursor to Windows Vista SP1. "Wow, lots of updates rolled into just two hot fixes," gushed a poster on a forum hosted by tech enthusiast site Neowin -- one of the Web sites that posted the leaked files.

To date, Microsoft has denied all reports that Windows Vista SP1 already exists. A spokesmen for the company recently told InformationWeek that Microsoft's official position on Vista SP1 is that it will be released sometime later this year.