SAN FRANCISCO - Microsoft on Wednesday released the Windows 8 Consumer Preview, offering the beta version of its next-generation operating system as a free download worldwide.

The Consumer Preview give consumers a close look at the upcoming Windows 8 retail version, which is designed to work on a wide range of devices, from touch-enabled tablets, to laptops, desktops and all-in-ones, according to Microsoft's official blog.

The company on Wednesday also shows off the system at the Mobile World Congress event in Barcelona, Spain.

The system is a follow-up to the Windows 8 Developer Preview, which has been available for free download since last September. Some 3.5 million copies of the developer version were downloaded and dozens of features and tweaks have been added to the Consumer Preview since then.

The Metro-style interface is one of the top features of Windows 8, filling the computer screen with colorful tiles that are especially designed for touchscreens and daily computer usage like browsing, social networking, photos, games and etc.

The traditional "Start" menu is replaced by a full-screen view of tiles that users can scroll through. Users can pin applications, shortcuts and anything they like to customize the interface.

Hiding on the right side of the screen is a set of so-called "charms" which give access to high-level system commands, including search, share, start, devices and settings.

Microsoft warns that the Consumer Preview is still "a work in progress." It noted that developers and anyone who try the new system will encounter some hiccups and bugs, and the company is looking for feedbacks.

To download the Consumer Preview, the computer should run on the same hardware that powers Windows 7. There are also some additional requirements for some certain features such as a higher resolution display or multitouch-capable screen.

Windows 8 marks the biggest change Microsoft has ever done to its operating system as worldwide users have been used to the Windows 95 style for 17 years.

"Windows 8 still feels like two very different operating systems trying to be one," said technology blog Engadget in a detailed review of the Consumer Preview. "The potential is hugely alluring -- a single OS to rule both the tablet and the desktop - and with each subsequent version we keep hoping this will be the one that ties it all together. Sadly, as of the Consumer Preview, we're still seeing a lot of loose threads."

The final version of Windows 8 is expected to be released in late 2012.