Over a month ago, we were briefed about a secret Microsoft technology that we were told would be announced alongside the Windows 7 Release Candidate (RC) and would ship in final form simultaneously with the final version of Windows 7. This technology, dubbed Windows XP Mode (XPM, formerly Virtual Windows XP or Virtual XP, VXP), dramatically changes the compatibility story for Windows 7 and, we believe, has serious implications for Windows development going forward. Here's what's happening.
XP Mode consists of the Virtual PC-based virtual environment and a fully licensed copy of Windows XP with Service Pack 3 (SP3). It will be made available, for free, to users of Windows 7 Professional, Enterprise, and Ultimate editions via a download from the Microsoft web site. (That is, it will not be included in the box with Windows 7, but is considered an out-of-band update, like Windows Live Essentials.) XPM works much like today's Virtual PC products, but with one important exception: As with the enterprise-based MED-V (Microsoft Enterprise Desktop Virtualization) product, XPM does not require you to run the virtual environment as a separate Windows desktop. Instead, as you install applications inside the virtual XP environment, they are published to the host (Windows 7) OS as well. (With shortcuts placed in the Start Menu.) That way, users can run Windows XP-based applications (like IE 6) alongside Windows 7 applications under a single desktop.