Following through on its promise to aggressively upgrade Windows 10 to subsequent product versions, Microsoft today is ending support for the original version of Windows 10.

That version, called Windows 10 version 1507, was released in July 2015, less than two years ago. But Microsoft now has an 18-month support policy for Windows 10 Home, Pro, Education, and Enterprise. (Microsoft extended this time frame by 60 days for version 1507.)

“After May 9, 2017, Windows 10 devices running version 1507 will no longer receive security and quality updates,” a Microsoft support document explains. “Microsoft recommends updating devices to the latest version of Windows 10.”

It’s highly unlikely—OK, near impossible–that any individual is still running this suddenly ancient and quaint version of Windows 10. But you can check your version number by typing WINKEY + R to bring up the Run dialog; then type winver and hit Enter.

“Since the initial release of Windows 10 in July 2015, Microsoft has released two additional feature updates that build upon each other, delivering the newest features and more comprehensive security,” Microsoft explains. “Windows 10 was designed [to be serviced] as a service, whereby feature updates are required a few times a year. For most consumers, both quality and feature updates are delivered automatically according to their Windows Update settings.”

If you continue to use Windows 10 version 1507, you will no longer receive new security updates or other quality updates, but Microsoft says the system will still operate.