Two substantial collections of Windows Vista hot-fixes leaked to the Internet after being offered to Windows Server 2008 beta testers this weekend.

Some are now speculating that the pair are actually the foundation of the future Service Pack 1 (SP1) release for the OS.

Labelled "Vista Performance and Reliability Pack" and "Vista Compatibility and Reliability Pack," the two updates feature a long list of non-security-related bug fixes, including those that improve Vista's resumption after sleep or hibernation, boost the speed of copying or moving large directories, prevent some memory corruption problems, bolster the reliability of systems upgraded from XP to Vista and increase compatibility with video drivers.

"These issues have been reported by customers using the Error Reporting service, product support or other means," the two packs' release notes said. "Installing this update will improve the performance and responsiveness of some scenarios, and improves reliability of Windows Vista in a variety of scenarios."

Some Vista users commenting on several of the blogs and forums covering the hot-fixes - a message thread on nVNews appeared to have been the first - theorised that the packs would be the core of SP1, the service pack Microsoft has been both reluctant to talk about and eager to downplay.

Some of the fixes called out in the release notes seem to point in that direction, since they describe issues and patches already posted to the Microsoft support site. The item pegged as "resolves an issue where a computer can lose its default Gateway address when resuming from sleep mode," for example, is likely the same as an April 24 Vista fix.

The AeroXperience site even posted results of early testing of the packs' performance. According to a write-up here, systems updated with the Vista Performance and Reliability Pack copied large-sized folders in less than half the time as unpatched machines.

As of Monday afternoon, the fix packs were still accessible on at least one non-Microsoft download site. The performance pack update weighed in at 10MB, while the compatibility pack was considerably smaller, at around 2MB.

Although it may seem odd that the fix packs were released to Windows Server 2008 testers, that operating system - scheduled to launch early next year - shares code, particularly in the kernel, with Vista.

Microsoft did not reply to a series of questions about the fix packs, whether they are part of an already ongoing test of Vista SP1, or whether they would be issued in an upcoming release from Microsoft Update. The company often uses the one-a-month security patch schedule to also roll out other hotfixes; the next date is August 14, two weeks from tomorrow.