The new build is available to a preselected set of technical beta testers only. The new release is designated as a "pre-RC1," or pre-Release Candidate 1, build. The build previews some of the new features and design changes that Microsoft will make available to millions of testers—probably some time next month—as part of the Vista RC1 build.

Microsoft officials did not respond by the time this article was published to questions as to what is new in the latest build.

Resource Library:

But a number of testers who downloaded the build in the early hours of Friday morning were impressed by the performance improvements that Microsoft had made to the latest Vista build.

"Performance is about 3x better so far on my Dell Inspiron 9300, and driver support is phenomenal!" blogged Matt Freestone on the Windows Connected blog.

"I didn't have a single device that didn't come through setup installed except for the sound card which hit Windows Update and immediately downloaded and installed the driver, and did NOT require a reboot before it began to function! Amazing! I think that is the first time I have ever seen a sound card driver install without requiring a reboot. Windows sidebar is less resource intensive, and the current gadgets, while still limited (still missing that elusive Windows Media Player gadget) are much more refined and nice to look at," Freestone continued.

Read the full story on Microsoft Watch: Tech Testers Get a New Windows Vista Build

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