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Microsoft is planning an event in San Francisco later this month to show off its early work on the next version of Windows, code-named Threshold.

The Sept. 30 event, which will be led by Windows executives Terry Myerson and Joe Belfiore, will talk about where Microsoft is investing and show off some of the features of the new operating system. The company also has early code it will make available, according to sources, but the test code is intended mainly for developers and businesses to begin their preparations.

Typically Microsoft needs several test versions and months of development to finalize a Windows update. This event is aimed at a business audience, though Microsoft is planning other gatherings over the next year, sources say, to talk about what the next version of Windows offers for different audiences.

Microsoft has also been trying to drum up excitement within the company.

The company offered the first glimpse of the next Windows at its Build developer conference in April, where it showed the ability to run new-style Windows 8 apps in the traditional desktop.

Microsoft also added the ability for developers to write universal applications that can run on Windows, Windows Phone and Xbox, a move expected to be a first step in bringing its phone and desktop operating systems more closely together.

Redmond has thus far said little about the next version and most of what it has detailed have been moves to address critiques of Windows 8 from those who prefer the traditional Windows interface. At the Sept. 30 event, the company is expected to talk about the path forward for the operating system.

Enterprise needs will also be a key focus of the San Francisco event.