LONDON (Reuters) — Microsoft Corp. rolled out Windows Vista at retailers in 70 countries yesterday, delivering a PC operating system that aims to better manage the explosion of digital media and protect users from the dangers of the Internet.The world's biggest software maker marked the launch of its first all-new Windows operating system in five years with a marketing blitz including commercials featuring basketball star Lebron James and appearances by Bill Gates, Microsoft chairman and most recognisable face.

"We have just begun to see what we can do," Gates said at an event at the British Library in London. "We will be taking entertainment to a whole new level ... even education we believe will be changed very dramatically."

Vista, which required a $6 billion investment from Microsoft, will be installed on more than 100 million PCs world-wide, according to research reports.

Gates strayed from the technology of the product to proclaim that Vista's capabilities would be used to put online Leonardo da Vinci's famous Codex Arundel and Codex Leicester notebooks, making available the artist's drawings, mirror writing and theories to the public.

The Codex Arundel is held at the library, while Gates owns the Codex Leicester after he paid $30 million for the manuscript in 1994.

Windows runs on more than 95 percent of the world's computers and the long-delayed new version is the first major release of a new Microsoft operating system since it introduced Windows XP in 2001.

Redmond, Washington-based Microsoft called Vista the most important release of its dominant operating system since Windows 95 more than a decade ago, when shoppers waited for hours to be among the first to run the new software.

Consumer interest of that magnitude seems unlikely since Vista is not the dramatic leap in technology of past releases, but the new Windows could ultimately be just as successful.

Microsoft Netherlands chief Theo Rinsema, at a separate launch event, said Microsoft would be "very content" if it could push PC sales up by 5 to 10 percent during the first six months after the Vista launch.

Electronics retail chain MediaMarkt said PC sales had been held back before the Vista introduction as consumers had delayed their purchase.

"Vista will be successful. It's been a long time since Microsoft introduced a new operating system. There are a lot of nice features that people will like," said Morningstar analyst Toan Tran.

The most obvious change is the new look. Vista's "Aero" interface uses 3-D graphics to create translucent windows that appear to float above the background screen.

Other changes are more subtle, such as improved security, search bars to help users find information easier and a new multimedia platform for digital video, music and pictures.

Apple Inc. calls Vista a copycat version of its Mac OS X Tiger operating system, which introduced many of those new features. The iPod maker plans to introduce a new operating system of its own later this year.

At the event in London some of the audience was left underwhelmed by Gates' brief overview of the new technology.

"They were talking about the 'wow' but I didn't really see anything to wow me," said cameraman Brad Cramer.

"I have a Mac and a lot of the things they showed us I could do a couple of years ago, so we'll have to wait and see how much of an improvement there is," he added.

Microsoft also drew criticism from environmentalists and consumer interests groups that Vista would force unnecessary purchases of computers that need more energy.

Because only about 15 percent of existing computers have memory and graphics cards powerful enough to run premium versions of Vista, most users will have to buy a new computer if they want to upgrade.

"There is a pent-up set of consumers who are going to get new PCs," Microsoft chief executive Steve Ballmer said in an interview on Monday. "We will see an uptick (in PC sales). Sales will be stronger than they otherwise would have been."