I seem to remember a year ago, I said that if I were to design Windows 7 it would have built-in virtualization to provide perfect Windows XP compatibility. Guess what? It will.
It's not often that my predictions come true almost exactly the way I envision them.
Just a little over a year ago, I wrote an article entitled "If I were to design Windows 7". In it, I describe a feature that would ease migration pains for home and enterprise users of the new operating system:
"I would make XP applications run out-of-the box without any additional software instead of putting the onus on the end-user to install a licensed copy of XP on the system, a la VMWare Workstation or Microsoft Virtual Server. All Microsoft needs to do is include a stripped-down XP virtualized subsystem that contains all the core Windows XP SP3 libraries and a fully Para-virtualized XP kernel, so that it will run on 32-bit systems as well as 64-bit Intel VT-accelerated and AMD-V enabled systems, with a “Seamless” way to present XP applications, perhaps via a internal RDP interface or a DirectX accelerated virtual video driver, without having to run a complete XP desktop."
Well well. It seems that a major new feature that is to appear in the soon to be released Windows 7 Release Candidate, Build 7100, will be perfect Windows XP compatability, using virtualization technology.
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Now, to be fair, Microsoft didn't implement the feature exactly as I described. I thought they would use the Hyper-V hardware assisted Type 1 hypervisor technology introduced with Windows Server 2008. But instead, they went with hardware-assisted host-based virtualization, using an embedded/runtime and updated version of Virtual PC, presumably limited to running just the XP compatability VM, a Type 2 hypervisor.Okay, not exactly the same, as Type 1 and Type 2 hypervisors have different performance and stability implications, but if you look at how they actually implemented it, it's fairly close to what I predicted -- it's an optimized XP SP3 desktop that can either run on the Windows 7 desktop in a windowed mode, or have Windows XP applications run "seamless" with Windows 7/Vista applications in the Windows 7 GUI.
Why is Microsoft doing this? Because they don't want to repeat the unmitigated disaster of Windows Vista, and to assure its Enterprise customers that their legacy Windows XP and earlier applications will continue to work perfectly in the new OS -- they know that with the lousy economy, not everyone is going to be upgrading all their applications to Windows 7 and Windows Vista native versions.
Windows XP Mode, or XPM for short, will be available to customers running the Professional, Enterprise, and Ultimate editions of Windows 7. Users of "Home Premium", the version which will be on the majority of mass OEM preloads for the consumer market, will not have access to this feature. While I applaud Microsoft for thinking of its Enterprise customers, I think it is a mistake to exclude their consumer and SOHO customers from this great new feature. I really hope they change their mind.
I would have also liked to have seen a way for users with existing PCs with already installed apps to be able to migrate their software to the XPM environment, in a scripted, painless way, without having to completely re-install everything. XPM requires that you have all of your original installation media or have download access to the programs you need to run on your virtual XP environment.
That's fine for an ideal world, but we all know that install media and entitlements get lost, so a P2V tool for XP to Windows 7 XPM would have been nice. I described a rather labor intensive procedure on how to manually do this on Vista using the free VMWare Player which I did for a friend back in September of last year. Microsoft could easily provide a virtual "lifeboat" to their XP install base with a program similar to VMware vCenter Converter which dumps the entire environment -- apps, data files and all -- to a .VHD file on a portable hard disk or over the network to the new machine.
I'm really looking forward to XP Mode in Windows 7. Are you also feeling better about the new OS knowing that all your old apps will run perfectly? Talk Back and Let Me Know.