That's a far cry from the company's goal of getting Windows 10 onto a billion devices within three years. Microsoft says it's releasing the software in waves to make sure downloads go smoothly.

In a blog post late Thursday, Microsoft said it has not yet delivered Windows 10 to everyone who requested a free upgrade for computers running older Windows versions. Microsoft says the 14 million includes some copies installed on new computers sold in stores.

Reaction has been mostly favorable, with reviewers calling the new Windows an improvement over the last version, known as Windows 8.

Replete with a redesigned web browser called Edge and Cortana, a Siri-like voice activated assistant, Microsoft is looking to recapture some of the market share lost to rivals Apple and Google and lay to rest the ghosts associated with its 2012 Windows 8 system, a news agency reported.

Microsoft, while retaining some of the features of its unpopular Windows 8, such as "live tiles" for touch-based computing, the company decided to forego the release of a 9th version and jumped straight to the release of 10.

The company said it had retained, fused and improved upon the best features from its more successful Windows 7 and Windows 8 instalments.

It also said its latest operating system had been designed to work across different hardware platforms, including personal computers, tablets and smartphones, its Xbox games console and HoloLens -- Microsoft's holographic headset.

Along with the innovative 'live tiles', Microsoft has upped its game by following its consumers' recommendations to bring pack the iconic 'Start' menu, after the company dropped it from its previous upgrade.

The software update will be free for one year, the company has confirmed, a move market insiders believe is a bid to better compete with Google and Apple, particularly in the burgeoning phone market.

The package is available as free upgrade for those currently using Windows 7 and Windows 8.1. Those using older versions will first have to first upgrade to 8.1 to get the free update. Those not eligible will be required to pay around USD 119 for Windows 10 Home and USD 199 for Windows 10 Pro.