Microsoft has backtracked on its decision to only offer Windows 7 machines with an XP downgrade option for six months.

Earlier this week, Gartner slammed Microsoft's plans, saying it was likely to become a "real mess".

As Windows 7's launch date is October 22, the six-month cap meant that OEMs would have to stop shipping PCs 'downgraded' from Windows 7 Professional or Windows 7 Ultimate to Windows XP Professional at or around April 22, 2010.

Gartner analyst Michael Silver said this would cause problems for large enterprises.

For an organisation that's trying to skip Vista, that means they really need to buy new PCs that they need to run on XP, and want to upgrade later to Windows 7, by April 21 2010," he said.

However, Microsoft has now confirmed it has a new downgrade policy in place.

"Windows 7 Professional and Ultimate customers will have the option to downgrade to Windows XP Professional from PCs that ship within 18 months following the general availability of Windows 7 or until the release of a Windows 7 service pack, whichever is sooner, and if a service pack is developed," a company spokeswoman said.

Silver said Microsoft's new policy was "good". "It proves that Microsoft listens to their customers. They have changed licensing decisions in response to customer demand before, and hopefully they will do it again, because this is still not great."

"The new policy is 18 months or SP1 delivery, whichever is sooner," he added. "It means that if SP1 shows up in six or eight months, the date suddenly moves in."

Many software vendors may not release Windows 7-specific versions or officially support the new operating system for a year or longer after Microsoft rolls out the OS this October, Silver added. Microsoft's movable deadline for the end of downgrades could put some enterprises in an awkward spot.

"Organisations waiting on a critical vendor to support their product under Windows 7 may still have a problem," he said.

A better solution would be a hard deadline, Silver said. "The policy should be 18 months or SP1, whichever is later, or just have a reasonable date for the end of the downgrade right, like December 31, 2010."