Microsoft on Thursday unveiled the latest of its test — or "preview" — versions of what it hopes will be a showstopper of an operating system expected to be released this fall.

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With this many previews, it’s like a new theatrical musical headed toward its Broadway debut.

Microsoft on Thursday unveiled the latest of its test — or “preview” — versions of what it hopes will be a showstopper of an operating system expected to be released this fall.

Called the Release Preview, it’s the final test version of Windows 8, Microsoft’s huge overhaul of its flagship operating system.

The Release Preview (available for download at follows the Technical Preview, unveiled last June; the Developer Preview, released in September; and the Consumer Preview, released in February.

Among the new features in the Release Preview are apps — including ones for travel, news and sports — powered by Bing; new and updated apps in the Windows Store; improvements to the Mail, Photos and People apps; and increased personalization options for the Start screen.

If the feedback on the Release Preview matches Microsoft’s expectations, Windows 8 will enter the “release to manufacturer” stage in about two months, Windows President Steven Sinofsky said in an official blog post Thursday.

“If we are successful in that, then we are tracking to our shared goal of having PCs with Windows 8 and Windows RT available for the holidays,” he wrote.

Media outlets and analysts have speculated that the final release date for Windows 8 will be in October.

Microsoft is betting big that Windows 8 will revive the company’s fortunes in the mobile market, where its tablet sales lag far behind Apple’s iPad, while maintaining its dominant position in the PC market.

It’s a risky bet.

That’s because Windows 8 is very different from its predecessors — seen, by some, as the biggest change in Microsoft’s operating system since it moved from MS-DOS to Windows.

Instead of traditional icons and a Start button, for instance, Windows 8 will use rectangular and square tiles and a Start screen. The goal, according to Microsoft, is for Windows 8 to be just as user-friendly on touch-based devices like tablets as it is on traditional mouse-and-keyboard-style computers.

Perhaps the break from tradition is what spurred Microsoft to give specific names to each of the Windows 8 test versions.

Previously, test versions of Windows have been referred to as “alpha,” “beta” (including possible multiples such as “beta 1” and “beta 2”) and “release candidate.”

The new names, from Technical Preview to the current Release Preview, may be giving the “signal that you’re using a new process,” said Michael Cherry, an analyst at the independent research firm Directions on Microsoft.

“As long as you’re re-imagining the operating system, why not re-imagine the process,” he said.

Microsoft may also want to distance itself from the process leading to the 2006 release of Windows Vista, in which high-level execs overpromised and underdelivered, Cherry said.

“Vista was wide open. They were maybe sharing too much stuff” — some of which didn’t end up in the final product, he said.

The information flow — and, hence, expectations — for Windows 8 has been much more controlled, Cherry said. “They do not want this to be another Vista.”

Information about changes in Windows 8 flow from one source: the Building Windows 8 blog written by Sinofsky and members of his team.

Though those blog posts have often been long they “leave as many questions unanswered as answered,” Cherry says.

One such unanswered question is where exactly in the development process is Windows RT.

Windows RT is the version of Windows that’s being designed to run on energy-efficient system-on-a-chip ARM-based processors that are commonly used in tablets and smartphones.

To complicate matters, both Windows 8 and Windows RT will be used in tablets. The Windows 8 tablets will run on Intel processors and be backward compatible with Windows 7 apps. Windows RT will run on ARM-based processors and won’t be backward compatible.

Sinofsky refers in Thursday’s blog post to having both Windows RT and Windows 8 ready in time for the holidays. But he and the company have not said whether Windows RT is in the Release Preview stage. And Windows RT test versions have never been available for public download since special hardware is required to run it.

As far as giving specific names to each test version, a Microsoft spokeswoman said it indicated to the public who the release targeted — developers or tech enthusiasts. The process being used for releasing information about Windows 8 is similar to the one used for Windows 7 — which was indeed a change from that used for Vista, she said.

Janet I. Tu: 206-464-2272 or On Twitter @janettu.