Upgrading Windows Vista Enterprise to Windows 7 Ultimate
I just performed an upgrade from my Vista Enterprise SP1 x64 bit to Windows 7 build 7000 on my Lenovo T500. The upgrade path from Enterprise edition to Ultimate is not supported but with a quick little registry fix it turned out to be a painless upgrade.
Prior to the upgrade change these settings:
HKLM\Software\Microsoft\Windows NT\Currentversion\EditionID (value Enterprise) to Ultimate
This should be enough to pass the prerequisite check and start the upgrade process.

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Dear Kent,
Thanks very much for this fix. I have five PCs — 2 are x86 and three are x64 — that have Windows 7 Enterprise Build 7600 installed, and I have purchased four Win 7 Professional licences and one Win 7 Ultimate “upgrades.”
My question is: do you know if the fix you have come up with for Win 7 Ultimate x64 will work for Win 7 Professional.
I’m going to try to implement your fix for Ultimate on my HP dv6-1050us that currently is running Win 7 “Enterprise” x64 Build 7600. It is the machine that I intended to install Ultimate on but could not do so because . . . well, you know!
Thanks for identifying this fix to a very vexing problem.
Best regards,
Michael Ebert