The updates, which are available now only through Microsoft's download centre, address performance and compatibility concerns with the operating system.

Microsoft isn't standing still with Windows Vista. The company Tuesday released two updates to address performance and compatibility concerns with the operating system and confirmed this week that Windows Vista SP1 is in early pre-beta testing with a "select group of testers."

After unauthorised versions of the two Vista updates appeared online last week and were quickly removed by Microsoft, they became public on Tuesday.

These fixes, available now only through Microsoft's download centre, will later become available through Microsoft Windows Update.

Next Tuesday is Patch Tuesday for Microsoft, so they could be available on Windows Update sooner than later.

The first update, KB938979, is a package of performance updates that deal with such problems as poor memory management, long calculation times for estimating the total time remaining on large file moves, memory leaks when using the Windows Energy screen saver and delays upon returning from hibernation or when exiting the Photos screen saver.

Some Vista users have complained of poor performance, so any fixes are likely much wanted additions. The first update also fixes file corruption problems when writing to AVI files, synchronising offline files to servers and editing image files that use the RAW image format.

The other update, KB938194, focuses on compatibility and reliability. For example, it addresses video and gaming graphics problems, printer spooler interruptions, screens blanking when external displays are turned off, display driver error messages and problems with diagnostics when the computer is under heavy usage.

Microsoft hasn't been tremendously open about the prospects for Windows Vista SP1, up until now only saying that it hoped to have a beta version of the service pack out by the end of the year and painting SP1 in the broadest of strokes, such as a fix to assuage Google's complaints about Vista's integrated search technology.

Though no new details have emerged on SP1's contents, Microsoft is confirming that a pre-beta version of Vista SP1 has been released to some testers, and that screen shots found on the Web this week are indeed of the elusive service pack.

The company apparently isn't done with Windows XP yet, either. Reports this week suggested that just as one group of testers got their hands on Vista SP1, another group began testing Windows XP SP3, which Microsoft has preliminary plans to release the first half of next year.

Microsoft on Wednesday confirmed those reports.

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