Microsoft has set Oct. 31 as the end of sales of new consumer-grade Windows 7 PCs, but for now has left open the do-not-sell-after-this-date for business machines.

On the site where it posts such policies, Microsoft now notes that Oct. 31, 2014, is the end-of-sales date for new PCs equipped with Windows 7 Home Basic, Home Premium or Ultimate. All three are consumer-oriented versions of Windows 7; Home Premium has been the overwhelming choice of OEMs (original equipment manufacturers) for consumer systems.

Microsoft's practice, first defined in 2010, is to stop selling an older operating system in retail one year after the launch of its successor, and halt delivery of the previous Windows edition to OEMs two years after a new version launches. The company shipped Windows 8, Windows 7's replacement, in October 2012.

The setting of a deadline for consumer Windows 7 PCs followed a glitch last year when Microsoft named the same Oct. 31 date for all Windows 7 PCs, but then quickly retracted the posting, claiming that the notification had been posted "in error."

Some OEMs, notably Hewlett-Packard, have made headlines for marketing consumer-grade Windows 7 PCs, a sign of the fragmentation of the once-dominant Windows oligarchy, which always pushed the newest at the expense of older editions.

But while it has established an end-of-sales date for consumer PCs with Windows 7 pre-installed, Microsoft has yet to do the same for business PCs.

Microsoft will give a one-year warning before it demands that OEMs stop selling PCs with Windows 7 Professional, the commercial-quality version. Under that rule, Microsoft will allow computer makers such as Lenovo, HP and Dell to continue selling PCs with Windows 7 Professional until at least February 2015.

It's likely that the extension will be much longer.

Windows 7 has become the standard version for businesses, which have spurned Windows 8, largely because of its two-user interface (UI) model, which they consider disruptive to productivity and a needless cost that would require employee retraining.

Most analysts believe that Windows 7 will remain the most popular Microsoft operating system deployed by companies for years to come.