Microsoft released on Thursday the final test version of its next-generation Windows software crafted to power devices ranging from tablets to desktop computers. “We’re thrilled to be at this milestone with the Windows 8 Release Preview,” said Windows and Windows Live division President Steven Sinofsky. The nearly finished Windows 8 software was available for download in 14 languages at preview.windows.com. Availability of Windows 8 Release Preview marks the final phase of development before the operating system becomes available to makers of computers and other devices. A “consumer preview” version of Windows 8 was downloaded more than a million times in the 24 hours after its release in February, according to Microsoft. Microsoft’s upcoming Windows 8 series — featuring an upgraded cloud computing service — marks a “rebirth” of its operating system, chief executive Steve Ballmer said last week at a gathering in South Korea. Ballmer described Windows 8 as the “deepest, broadest and most impactful” Windows software ever created by the Redmond, Washington-based tech giant, after the current Windows 7 sold at unprecedented rates to businesses. “It’s really, in some senses, a dawning of the rebirth of MS Windows... It’s certainly the most important piece of work we’ve done,” he said in a speech to the Seoul Digital Forum. Windows 8 allows users readily to store and share personal data among various devices under the “SkyDrive” cloud computing service. Rivals Apple and Google offer such services. The new Microsoft system will support a wider range of devices, including touch- and stylus-based smartphones and tablet PCs as well as desktop and laptop machines, Ballmer said.