Microsoft has released a preview of its upcoming Windows 8.

Microsoft president Steven Sinofsky introduced the final Windows 8 preview release for developers, the final version of which will  go on sale later this year. Sinofsky said that since Microsoft's first preview release last September, millions of people now use the pre-release product on a daily basis and millions more have been taking it through its paces, totaling hundreds of millions of hours of testing.

Visible changes include the obvious move towards tablet computers, with the Metro interface, and the apps and Windows Store mentioned above. Sinofsky said that this is only the beginning of changes, adding that the design of Windows 8 will bring about an evolution in PCs.

"As we reimagine Windows from the chipset to the experience - new hardware support, new user interaction models, new scenarios, new APIs and more, are all enabled with Windows 8, while we bring forward and improve the way Windows 7 has been used on over 550 million PCs around the world," he said. "Coming soon, we will see a new wave of PCs designed for Windows 8, along with new apps powered by the new Windows 8 platform," he added.