If you get a PC running Windows 7 but can't divorce yourself from Windows XP, Microsoft will give you 18 months to downgrade - not six.

That's the line from Microsoft, which said that downgrade rights will be available from the date Windows 7 ships - October 22, 2009 - to April 1, 2011.

Downgrades cover just two editions of the impending operating system, for consumers and small businesses. You can only move from Windows 7 Professional to Windows Vista Business or Windows XP Professional, and from Windows 7 Ultimate to Windows Vista Ultimate or Windows XP Professional.

Organizations with Windows volume license, which cover 250 PCs or more, will be able to downgrade to any prior version of Windows - a standard policy.

But the downgrade window will expire before 18 months if a service pack ships. Downgrade rights to Windows Vista will not expire.

Microsoft confirmed the stance for The Reg in the wake of a report by Redmond Channel Partner.

That came after long-time Microsoft watcher Michael Silver of Gartner was said the company had discussed a six-month limit on downgrades from Windows 7 with him "multiple times and characterized it to him as a 'public' policy'." ®