Why did Windows XP rise from the grave? To help Windows 7 sales.

Microsoft's announcement yesterday that it has extended Windows XP's life yet again by allowing downgrades to it from Windows 7 until 2020 sounds like a step back for Microsoft. In fact, though, it's a canny move to get enterprises to buy Windows 7 now rather than later.

The extension of downgrade rights to XP applies only to those who buy Windows 7 Professional and Ultimate. Downgrade rights allows people to replace their newer version Windows with an older one, without having to pay for two copies. As Gregg Keizer reports in Computerworld, these downgrade rights are typical allowed only for a very short amount of time, and are killed within months of when a new version of Windows is released.

That hasn't been the case with downgrade rights to XP, because it's the operating system that refuses to die. The only way many people and enterprises seem willing to give up XP is to have the operating system pried away from their cold, dead hands. Because of that, Microsoft has several times been forced to change downgrade rights to XP from newer operating systems.

Originally, Windows 7 users had only six months in which they could downgrade to XP. Then Microsoft relented and said downgrade rights would be extended either until 18 months after Windows 7's debut in October, 2009, or until the release of Windows 7 SP1.

That meant the downgrade rights would end in 2011, possibly in April.

Yesterday, all that changed. Microsoft yesterday announced the availability of a beta of Windows 7 SP1 and extended downgrade rights from Windows 7 to XP. In the announcement on a Microsoft blog, Microsoft spokesman Brandon LeBlanc had this explanation about the extension of downgrade rights:

Our business customers have told us that the removing end-user downgrade rights to Windows XP Professional could be confusing, given the rights change would be made for new PCs preinstalled with Windows 7 and managing a hybrid environment with PCs that have different end-user rights based on date of purchase would be challenging to track.

Later on, he wrote:

To support our customers' "unprecedented move" to migrate their PC environment to Windows 7, we have decided to extend downgrade rights to Windows XP Professional beyond the previously planned end date at Windows 7 SP1. This will help maintain consistency for downgrade rights throughout the Windows 7 lifecycle.

They key to understanding all this is that despite what Microsoft says about booming Windows 7 sales, Windows XP remains the enterprise stalwart. Yesterday, Microsoft's Corporate VP of Windows, Tammi Reller, told the Windows Partner Conference that 74 percent of business PCs run Windows XP, not Vista or Windows 7, according to Electronista.

Microsoft, of course, wants all those businesses to pay to upgrade to Windows 7, and now rather than later. But not all businesses want to do a massive, immediate upgrade to Windows 7. Instead, they're prefer a more gradual approach, one that won't disrupt their business. Given a choice between a massive upgrade and staying with Windows XP, they'll opt to stay with XP.

The extension of XP downgrade rights for essentially the entire life cycle of Windows 7 allows them to gradually upgrade. They can buy Windows 7 now, which puts money in Microsoft's coffers, but use downgrade rights to keep as many machines on XP as they want. That way, they're in control of how fast or slow they upgrade to Windows 7.

The stability of Windows XP continues to haunt Microsoft, because many businesses still have yet to upgrade from it. But the new Windows 7 downgrade rules may get them to move to Windows 7 sooner rather than later.

Copyright © 2010 IDG Communications, Inc.

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