Comprehensive support for Microsoft's Windows 7 desktop and laptop operating system will end today, with no more free phone and online help available to users.
Microsoft will only provide updates with direct security implications from now on, for the next five years.
While Microsoft red-lined retail stand-alone sales of all editions of Windows 7 by October 2013 and asked its partners not to sell PCs pre-installed with the lower specification versions of the operating system after October last year, vendors can still continue to ship systems running the top-end Windows 7 Professional product.
Windows 7 remains the most-used desktop operating system in the world, according to analyst firm NetApplications, with over 56 percent market share as of December last year.
The newer Windows versions 8 and 8.1, both with a radically different user interface compared to Windows XP and 7, have not been as well received by users.
Mainstream support for Windows 8 will end on January 10 2018, with extended support finishing in 2023.
The end of support dates for Windows 8.1 have not yet been decided by Microsoft.
Microsoft is expected to release Windows 10, the successor to Windows 8.1, this year.