Vista Virtualization

At today's launch event in Greensboro, several people came up to me during the session breaks to get clarification on Vista's virtualization restrictions.  I admit, this area is really confusing and I thought I'd blog some thoughts on the topic.  As with everything else on this site (but particularly here) this is my understanding only and intended for guidance, and not representative of any official policy by Microsoft. 

Let's get one confusing topic out of the way first: Vista supports a virtualization feature as part of UAC (User Account Control).  UAC is important because it helps reduce the attack surface by requiring explicit elevation in privilege when an application needs administrator permissions.  In some cases, applications (particularly legacy applications) may not have been tested or developed with UAC in mind, so Vista incorporates some virtualization features to ensure these applications work.  These virtualization features essentially redirect IO and registry calls to a private virtual store and "fools" the apps into thinking they are writing to the real McCoy.

Why is this confusing?  Well, when we first mention some great new virtualization features, many folks have flashbacks to reading about certain restrictions regarding virtualization of Vista.  In this case, this virtualization refers to running Vista in a VPC or other virtual environment.  OK, with that out of the way...

So what's the issue?  The original Vista EULAs were quite restrictive with how you could install Vista in a virtual environment.  Much of this has changed for the better, but many are still confused.  The question I got a couple times today was phrased something like, "I can't run Vista Home in a virtual environment?  What if I want to test my app on Vista Home?"

The short answer is:  MSDN licenses are quite a bit more liberal with what you can and cannot do.  Assuming you're developing an application and targeting multiple operating systems, odds are you'd have an MSDN license (they are cheaper, after all, than buying all the components separately).  With an MSDN license, you're really only restricted by the general theme of not using the tools in a production system. 

The terms get a bit more strict in the OEM and retail edition space, particular with Vista Home.  These editions are generally targeted for the end-user or, in some cases, specific machines with OEM editions.  Hence, the terms are bit more strict.

Some licenses (such as Vista Enterprise or, in some cases, Vista Ultimate) allow up to 4 copies to be installed in a virtual environment with a single license.  It should be noted, too, that there's no specific need to use Microsoft's Virtual PC -- though, a new version (Virtual PC 2007) will be out soon and will be free, too.  (Virtual Server, however, will -- as far as I know -- not be free.)

In conclusion, there are some new restrictions in place that muddy the waters, but overall, the licensing is more liberal for most developers.  If you must run Vista Home virtualized, do so with an MSDN license. 
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