Microsoft announced this morning extended support through 2014 for consumer versions of Windows XP, the operating system that Windows Vista will replace when it's released on Tuesday.
The extended support for Windows XP Home and Media Center editions does not affect the existing mainstream support period, which ends in April 2009. The change brings the consumer editions in line with Microsoft's support policy for Windows XP Professional and other products.
The differences between what's covered by mainstream and extended support are detailed here. Basically, you have to pay for more stuff during the extended support period.