Aimed at winning back some ground lost to Apple and Google in the operating systems arena, Windows 8 is designed to work on tablets as well as PCs and laptops to give users a more consistent experience when switching between devices, CNN reported.
"It's beautiful, modern, fast and fluid -- it's a generational change in the Windows operating system," Microsoft Windows President Steven Sinofsky said in launching the consumer preview edition.
Windows 8 seamlessly scales across devices and screen sizes, Sinofsky said.
"There's too many hard stops between phones and tablets and desktops. We want to make things more harmonious," he said.
To that end the new operating system uses the "Metro" style of software currently featured on Windows phones, using a tiled startup screen.
Some tech-industry analysts said Windows 8 was unlikely to do that much for Microsoft's market profile, but moving into the tablet arena was crucial for sustained relevance.
"Microsoft needs to be in the tablet game," London-based analyst James Governor said. "It couldn't sit out two or three rounds of tablets without trying to have a more effective play and clearly Windows 8 is a big part of that."
However, he said, the popularity of Windows 7 suggests there won't be a huge surge of people wanting the update for desktop and laptop computing.
"I don't think it's an explosive 'Christ, we've got to have this new release,'" he said. "There isn't necessarily a pent-up demand for what Windows 8 represents."