Why won't Microsoft allow home/end-user versions of Vista to be virtualized (run in a simulator such as EMC's VMware)? Mostly this is a theoretical argument not related to Copyfight, but on Sunday Eric Lai published a column for Computerworld in which he suggests that the reason is that virtual environments may permit people to circumvent Vista's DRM.

You may recall that Vista contains the first commercial incarnation of MSFT's built-in control facility for restricting what programs and data can be installed and run on PCs. Virtual machines can unintentionally fool, block, or thwart various of the checks that DRM software uses. Lai references unnamed "analysts" to suggest that concerns over DRM circumvention were behind Microsoft's sudden change of heart. Apparently they were about to relax the prohibition on virtualizing Vista Home editions then suddenly stopped.

Not so fast, says Ken Fisher over at ars technica. He lists a couple of reasons why he doesn't believe Lai's theory, not least of which is that there's no technical reason blocking virtualization now. It's purely a license-terms issue.

Fisher thinks it's a step in the Microsoft-Apple war, with MSFT trying to defend its OS revenue stream. Could be. I do think Fisher's points are telling, to the extent that those of us who care about DRM and what Microsoft are doing in that area can safely ignore the virtualization debate.