Microsoft launched a radical redesign of its world-dominating Windows operating system Thursday, introducing a touch-enabled interface that attempts to bridge the gap between personal computers and fast-growing mobile devices powered by the company’s fiercest competitors.

The debut of Windows 8 heralded the biggest change to the system since 1995, when the company first offered built-in Internet support. And with so much riding on it, the overhaul could be Microsoft’s most important product since co-founder Bill Gates won the contract to build an operating system for IBM Corp.’s first PC in 1981.

To succeed, the new version will have to be innovative and elegant enough to attract consumers who’ve fallen in love with notebook computers, tablets and smartphones running software from Apple and Google.