Windows Vista has been shifted into what Microsoft calls extended support.

Vista, the problem-plagued operating system that never really took hold among users, will exit mainstream support today.

In a product's extended support phrase, Microsoft continues to provide security patches to all users, but offers other fixes - such as reliability and stability updates - only to organisations that have signed support contracts with the company.

Just seven weeks ago, Microsoft extended support for the consumer versions of Windows Vista - as well as Windows 7 - by five years to synchronise their support lifecycle with that of the comparable enterprise editions.

Previously, Microsoft had committed to supporting consumer software with security updates for just five years, not the 10 granted to business software.

Vista's last major update was Service Pack 2 (SP2), which debuted in May 2009.

Windows Vista's share of in-use operating systems has fallen dramatically since Microsoft introduced Windows 7 in October 2009. By the calculations of web metrics firm Net Applications, Vista now accounts for just 7.7% of all operating systems, and 8.3% of the machines running Windows.

Vista peaked at 19.1% in October 2009 and has been falling ever since. At the rate of its decline over the last 12 months, Vista will slip under the 5% bar in January 2013.

Vista will continue to run, of course: The migration into extended support does not make them inoperable. Microsoft will deliver security updates for Vista until mid-April 2017.

Vista users will be able to upgrade their PCs to Windows 8 when it ships later this year.