Existing PC users who are on Windows 7 and Windows 8 will get a free upgrade to Windows 10 - as long as they install this next version of Microsoft's computer operating system (OS) within the first year of the software's release.
It is the first time that the United States-based tech giant has offered a free upgrade on its flagship OS, which currently powers over 90 per cent of the world's computers.
What remains unknown after yesterday's announcement is how much Windows 10 will cost for new users or existing ones who upgrade to the new OS after the first year.
Microsoft skipped a number and leaped from Windows 8 to Windows 10 as it felt that the new OS was a significant leap forward. It is expected to launch globally in the second half of this year.
Users who own Windows Phone 8.1 smartphones will also get a free upgrade to Windows 10 within the first year.
Running the same OS across smartphones, tablets, PCs and its Xbox One game console is Microsoft's new strategy to get a leg up in the battle for market share in devices, especially smartphones and tablets where it lags behind rivals Apple and Google.
Microsoft chief executive Satya Nadella said: "Our ambition is for the 1.5 billion people who are using Windows today to fall in love with Windows 10, and for billions more to decide to make Windows home."