The clock is ticking on the demise of some downgrade rights for Windows 7, an analyst said Thursday.

Last year, Microsoft said that customers could downgrade new machines purchased with Windows 7 Professional to the older Windows XP Professional for a limited period. The deal ends 18 months after the introduction of Windows 7 -- in other words, in late April 2011 -- or when Microsoft launches Windows 7 Service Pack 1 (SP1), whichever comes first.

Nearly two months ago, Microsoft acknowledged it's working on Windows 7 SP1. It has not yet set a release timetable, however.

"So the clock is ticking down on that offer, after which time the only option for non-Software Assurance customers to deploy Windows XP is to use Windows XP Mode," said Al Gillen, an analyst with IDC, referring to Windows 7 Professional's built-in virtualized version of Windows XP.

Corporations that subscribe to Software Assurance (SA) -- MIcrosoft's annuity-like upgrade guarantee program -- or purchase Windows through volume licensing plans have downgrade rights from any edition, including Windows 7, to any previous version going as far back as Windows 95.

Full story: Computerworld