Microsoft launched its much-awaited Windows 10 operating system at midnight.
Windows 10, which comes almost three years after the launch of the company's last operating system, will be available as a free upgrade in 190 countries for users of Windows 7, Windows 8.1 and Windows Phone 8.1 operating systems, the company said.
The new operating system is designed to work across laptops, desktop and smartphones and is part of chief executive Satya Nadella's push towards winning back lost ground in the tablets and mobile arena.
The software features a new web browser - Edge - as well as a digital personal assistant called Cortana.
Microsoft also opted to bring back its iconic 'Start' menu as part of the operating system, following complaints over its removal in Windows 8.
Windows is by far the company's most important product, though it has decided to give it away for free to existing customers in order to grow its market share rapidly.
Last week, Chief Financial Officer Amy Hood said the company was looking to instead generate revenue by building search and gaming capabilities into the Windows 10 interface.
