Posted by: kurtsh | April 25, 2009

NEWS: Windows 7’s secret feature… “Windows XP Mode”

Well, looks like the cat’s out of the bag.  Virtual XP lives.  And it’s gonna be free and ready to deploy with Windows 7 desktops.  Completely free.  

For those that know MDOP, think of it as MED-V for consumers.

For Enterprise IT professionals familiar with Microsoft’s Enterprise Desktop Virtualization solution (a.k.a. MED-V, formerly “Kidaro”) you’ll find “Windows XP Mode” very familiar. 

Essentially with MED-V, you run compatibility-challenged applications within a local Windows XP virtual machine on Windows Vista however this differs from simply using Virtual PC 2007 in several very important ways.  The biggest most noticeable difference is that the application running within a virtual machine is bordered with a RED outline, and the rest of the Windows XP virtual machine is completely invisible to the user.

imageMicrosoft Enterprise Desktop Virtualization (MED-V)
See my demo MEDV above,  Notice the RED OUTLINE around Word 2002 running within the XP virtual machine.  The rest of the XP virtual machine is “hidden” by MED-V.

There are other benefits from MED-V including centralized change control, byte-level differencing, etc.  but from a visibility standpoint, this is the benefit most people see.

“Windows XP Mode” (XPM) from an end user experience is very similar.  XPM provides:

  • the ability to install applications into Windows 7 however funnel the installation & files into a local Windows XP virtual machine
  • the capability of running that application directly from a shortcut within Windows 7’s START menu and have it appear on the Windows 7 desktop as a standard application window, while in reality, it’s running within the XP virtual machine

In this manner, “Windows XP mode” is similar to MED-V however, XPM does NOT have a RED outline around applications running within XPM.

image Windows 7 “Windows XP Mode”
Word 2003 running within an “invisible” virtual machine, along side Word 2007 running natively
If nothing looks unusual in the above image… good!  Then we’re doing our job well.

As you can see the photo above(taken from Paul Thurrott’s site – no point in reinventing the wheel here) the same scenario of showing two versions of Word running at the same time each looking like their running within Windows 7 natively when in reality Word 2003 is running seamlessly within a virtual machine.

Essentially “Windows XP Mode” will be an “OOB” or an “out-of-band” released product that will be downloadable for licensed users of the business editions of Windows 7 – namely Professional, Enterprise, and Ultimate.

It will ship with a fully licensed copy of Windows XP with SP3 to allow end users to legally run Windows XP within Windows 7 without relicensing the OS.

Besides the obvious ability to run applications that require Windows XP to execute, Paul Thurrott points out the primary reason for Windows XP Mode:  By isolating all legacy compatibility functions into an optionally installable virtual machine, compatibility hooks for applications don’t need to exist in the core OS.

The fact is, all those legacy APIs & libraries from previous revisions of Windows burden the OS when in reality, only folks with compatibility issues need them.  The majority of people will use applications that have no need for Windows XP compatibility so why include it in EVERY DEPLOYED COPY OF WINDOWS 7?

By making Windows XP Mode an optional virtual machine, Windows 7 becomes lighter and cleaner than it’s predecessors.


Before certain individuals start crowing that Mac OS X had this capability years ago with Mac OS 9, to be clear – this is nothing like that.  This is complete hardware virtualization and dramatically more advanced work than what Mac OS X did to execute legacy applications due to the simple fact that Windows XP was and remains a much more advanced OS that Mac OS 9 classic.

For example, Mac OS 9 never had preemptive multitasking nor did it have memory protection, capabilities that were both available all the way back in Windows 95.  Mac OS 9’s time slicing and memory model across applications was more accurately the same as CPU time allocation and memory management within Windows for Workgroups 3.1.  A more appropriate analogy would be the execution of 16-bit Windows 3.1 applications within Windows NT 3.1’s WoW subsystem.

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