Microsoft has revealed that Windows 7 will offer an optional, downloadable Windows XP virtual machine to provide full backwards compatibility. Veteran Windows watchers Rafael Rivera and Paul Thurrott of SuperSite for Windows were given the nod to release the secret. Microsoft's Windows Team blog later confirmed the feature.
The Windows XP Mode won't ship with Windows 7, but will be available as a free download for Professional, Enterprise, and Ultimate system owners. The XP mode will comprise a Virtual PC 7 virtual machine and a fully licensed copy of Windows XP Service Pack 3. While this might weigh in at a couple of gigabytes, that's no longer an onerous one-time download even for many home users. (I have to download nearly a gigabyte of Leopard updates if I install Mac OS X 10.5.0 on a new hard disk.)
Windows XP Mode will be a separate environment, but will allow running programs to appear alongside Windows 7 programs, rather than locking them inside a window - this sounds just like the Coherence mode that Parallels initially introduced for Windows applications running under Parallels Desktop in Mac OS X; VMware later matched Coherence with VMware Fusion's Unity mode (see "Parallels Desktop Ups the Ante," 2006-12-04, and "VMware Announces Fusion 1.0 Release," 2007-08-06).
The strategy is clear. Including XP in a virtual machine enables XP users to make an immediate leap to Windows 7, buying new hardware that will run XP far faster, while preserving a functionally identical operating environment (one that's likely to be more stable and portable, too). Microsoft can break all the compatibility it wants with Windows XP (and perhaps Vista, too) in Windows 7, jettisoning old code, obsolete programming hooks, and other detritus.
Last year, I wondered why Microsoft hadn't simply coupled its Virtual PC division with XP for the release of Vista in "Microsoft Needs to Empty Windows Trash, Reboot" (2008-06-29) when I recounted how many times Apple repackaged compatibility layers and virtual machines as it cast off successive older operating systems or architectures. Apparently, I wasn't alone in asking that question.
This is a brilliant move for Microsoft, and one that's somewhat out of keeping with a company that has made backwards compatibility one of the hallmarks of how it moves forward. The move may provide a compelling carrot to firms and individuals who are concerned about upgrading applications but might want to take advantage of some of the advances in Windows 7.