Microsoft is ending mainstream support for Windows 7 at midnight tonight, potentially affecting 56 per cent of PC users.
Redmond will no longer issue improvements to the Windows 7 operating system, but will continue to provide security patches for another five years.
The expiration comes just nine months after Microsoft killed software updates and security patches for its XP operating system, and only six months before it ends support for Windows Server 2003.
Microsoft had wanted XP users to consider Windows 8 when migrating, but Windows 7 proved a more popular destination.
The latest NetMarketShare figures show that 56 per cent of all PC users were on the Windows 7 OS last month, up from 49 per cent of users back in April 2014, when XP support expired.
Windows XP still accounts for 18 per cent of all PC operating systems, but the much-maligned Windows 8 holds just four per cent of the market.
It was widely criticised for trying to act as both a desktop OS and a touchscreen OS.
Nearly 10 per cent of PC users run Windows 8.1, the improved successor to Windows 8.
Microsoft is now pushing its Windows 10 operating system, with a big announcement scheduled for January 21.
The OS is currently in Technical Preview, but a leak reveals a future version could include a Cortana search bar, a new Xbox app and an updated interface.
