A year after Windows 10 was made available for download for free, it has secured over one-fifth of the market share.

Net Applications said 20 per cent of computers are running on Microsoft’s latest operating system, which will now cost money to download.

In the first four weeks after its release, Windows 10 was installed on over 75 million PCs. 110 million devices were running on it 10 weeks in, followed by 200 million in six months, 270 million in eight months and 300 million in nine months, with the 350 million mark being hit after 11 months.

Microsoft was aiming to get its ‘final’ operating system Windows 10 on to a billion devices by 2018 but revised that goal as its Windows phone business nosedived.

Less than three per cent of smartphones have the Windows operating system.

There was a rush to download Windows 10 before the cut-off at the end of July, but there is a loophole which continues to allow users to get it for free.

It is still available for those who use assistive technologies – features which help those with potentially impaired vision or hearing.

Deemed by some an unethical way of procuring the free upgrade, Microsoft appears not to undertake any checks when users select the download.

For those with scruples, Windows 10 will now cost £99.99 for the home version and £189.99 for the professional version.

Windows 7 remains in top spot for Microsoft, holding 47.01 per cent of the company’s market stronghold.

In total, Microsoft operating systems form the majority of the market with a whopping 89.79 per cent, leaving Mac with 7.87 per cent and Linux with 2.33 per cent. 

Microsoft intends Windows 10 to be its final OS, with updates arriving from time to time as it moves to a Software as a Service model.

The firm announced last month that it is to buy professional social network LinkedIn for $26.2 billion.