There were two Vista service packs. Support for the first ended Tuesday, while Service Pack 2 will continue to receive mainstream support until April 10, 2012, and the more limited "extended support" until April 11, 2017. Once support for a service pack ends, that software no longer receives updates.

In the , Microsoft said: "We recommend folks look at upgrading to Windows 7, which is the fastest selling operating system in history, selling over 400 million licenses to-date. Windows Vista users can also use Windows Update to update their PC to the latest service pack available which is Service Pack 2 (SP2)."

The end-of-support dates follow published Microsoft policies and so are known months or even years in advance.

Just because your software is out of date doesn't mean you need to buy a new computer. A Vista machine, of course, can upgrade to the second Service Pack for free. Many Vista machines have the hardware necessary to upgrade to Windows 7, and this week Microsoft said any PC capable of running Windows 7 .