I always wondered if their was something in the registry for this kind of thing. All I can think of is maybe an upgrade install, but I don't know if you can do that. I doubt it for going from ultimate to pro.
Last edited by Petey7; 03 Aug 2010 at 14:11.
Putting "Pirated" in your headline (even erroneously) is like yelling fire in this theater and somewhat reckless, so please tell us where the Ultimate installer and your Professional Product key were obtained.
If you know that the installer is legitimately obtained and therefore safe to use, you can indeed change from Ultimate to Professional to use your Pro Product Key, employing a popular workaround used by many to change successfully from the RC to retail Win7.
Unlock Win7 Professional version in your Ultimate Installer if necessary by extracting the ISO using ImgBurn, then run the ei.cfg removal tool to unlock all versions, burn to DVD.
Change the two registry keys exactly as shown below which tricks the installer into thinking it is doing an always-allowed same version Repair Install:
Once the keys are changed to read exactly as they do here, back up your files and a Win7 Backup Image externally, run a Professional Upgrade install from Ultimate desktop, then activate at Computer>Properties with your Pro key.
It is not possible to "downgrade" with a product key, so as unfortunate as it may be, you're going to have to install Win7 Professional on that PC to activate it with a Win7 Professional key.
Last edited by cluberti; 04 Aug 2010 at 07:40. Reason: spelling
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I did get a not genuine watermark at first, but once I activated with my original Home Premium product code all was fine and legal again.