Struggling for a toehold in the booming mobile device sector and looking to maintain its PC systems' dominance in the face of an Apple onslaught, Microsoft is rolling out Windows 10 - a fresh version of its flagship operating system.The update to be issued Wednesday will establish a single platform for use across cellphones, tablets and PCs, in a strategic bid for mobile relevance, as well as replace the unpopular Windows 8, which bombed on introduction in 2012.Windows 10 is hoping for a reboot, with original features including a new web browser, Windows Edge and an expanded role for Cortana - a voice-controlled digital assistant Microsoft launched for smartphones as an answer to Apple's mobile digital assistant, Siri. Unlike Siri, which is only a part of Apple's mobile iOS operating systems, Cortana will be integrated across the Windows 10 platform, on desktop PCs, tablets and Windows smartphones. In a video posted online introducing the update, Microsoft touted the new features while emphasizing that Windows users would find it easy to adapt to the changes."It's still the desktop you love, only better," one caption read - in apparent reference to Windows 8, which many users panned for its radical redo of the desktop interface. For decades, Windows operating systems have been a nearly ubiquitous part of computing around the world. As of last month, more than 90 percent of the world's desktop computers used some version of the Windows operating systems, according to market analysis firm NetMarketShare.com. Fifty-four percent used Microsoft's Internet Explorer browser, for instance, but the company has barely scratched the surface of the booming mobile device sector, with just 2.3 percent of the market using the Windows Phone platform.At the same time, the PC market that Windows dominates is waning, with sales down 10 percent in the last quarter, according to Time magazine.Microsoft reported its worst quarterly results ever on July 21, due largely to its ill-fated attempt to build a market for Windows-based smartphones by acquiring Nokia's handset business, which it has now abandoned.But the company has committed to increasing Windows' share of the increasingly vital mobile device market, in part by making the system portable from Windows PCs users already own to smartphones and tablets they could buy because of it. Microsoft CEO Satya Nadella has said he wants to have 1 billion Windows-powered devices on the market by mid-2018. Windows 10 launches at midnight Tuesday on the east coast of the U.S. (04:00 GMT on Wednesday). Microsoft plans to roll out updates in small groups, starting with users who pre-registered months ago, so many users will have to wait weeks to try it out.