According to the HP communique, Microsoft will also discontinue the downgrade from Windows 7 Professional to XP Professional on April 30, 2010.

In a reply to follow-up questions, the Microsoft spokesman denied that any termination date had been set for Windows 7 downgrades, but implicitly acknowledged that they would be available for at least a time. "No dates have been announced for the end of Windows 7 downgrade right facilitation to Windows XP," she said.

If the HP memo is accurate, Windows XP will be available for more than a year after Microsoft shifts the aged operating system out of what it calls mainstream support, and into the more limited extended support phase. Windows XP will April 14.

HP did not immediately reply to a request for comment on the XP extension.