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Currently I've got an installation of Windows 7 Ultimate x64. I would like to downgrade to Windows 7 Home Premium x64 without a clean install. I've got a (legal) retail disc and tried the following tricks:

1) Trick the Windows version using a registry hack with all possible combinations

2) In combination with a trick to make an ISO with all editions

Still the Windows setup keeps telling me I can't upgrade because I've got a higher version installed (Ultimate). The trick seems dead. Does anyone know a way to change from Ultimate to Home Premium without the hassle of a clean install?

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any particular reason for doing this ? –  Journeyman Geek Apr 28 '11 at 13:49
    
Licensing issues. Only valid license is the Home Premium one, the other one is expired. –  Mark Apr 28 '11 at 17:05
    
Someone else got a suggestion? –  Mark May 1 '11 at 18:17
    
I've always thought doing a clean install of Windows 7 is pretty quick and painless. Unless you have a space issue your existing install will be preserved in a "windows.old" file - useful if you forgot to back something up. You would be back up and running in a couple of hours. You can even get media with SP1 included from digital river –  BJ292 Mar 17 '13 at 22:50
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3 Answers 3

Windows 7 Ultimate is a superset of Home Premium, so no need exists to ever downgrade aside from licensing issues. You can change the Windows Components by going to "Start | Control Panel | Programs and Features | Turn Windows Features on or off" to remove those components included in Ultimate but not in Home Premium , effectively downgrading to the desirable version.

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Thnx! It's because of licensing issues indeed. So if I get this right the version is then stripped, but still says "ultimate". Would it work then if I change the license key to the Home Premium one? –  Mark Apr 28 '11 at 17:04
    
Things like AppLocker or BitLocker are not in the "Turn Windows Features on or off" screen. There are no "Ultimate" features to turn off. –  Mark Apr 29 '11 at 9:05
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It is possible and I have done it. I went from x64 RC (Ultimate) to x64 Professional RTM, from there to Ultimate via Anytime Upgrade now I am back to Professional. Don't ask me why I upgraded to Ultimate in the first place

Here's how I did it: You need your RTM files with the usual suspects (ei.cfg either removed or modified with the version you want to install, in cversion.ini file the minversion edited to sth lower than the current version, i have put 7000 there). Then in the registry go to local_machine -> software -> microsoft -> windows nt -> currentversion and set currentbuild and currentbuildnumber to 7100. Replace "Ultimate" in EditionID and ProductName with "Professional" (or whatever you wanna install or the name of a SKU lower than that).

Now you can start the Win7 Setup and chose upgrade. This way it is possible to "downgrade" your version of Windows 7 without the need to reinstall everything again!

Source of Information

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Thnx, will try this tomorrow. –  Mark Apr 28 '11 at 20:27
    
I tried it, but it didn't work. Also modified the keys in the Wow6432Node branche. Modified the ei.cfg and changed the cversion.ini. Still doesn't work, same message in setup. Maybe MS disabled this workaround? :( –  Mark Apr 29 '11 at 7:49
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Just Install right over it it is very easy get a cd pop it in and just install it using the "Customized" option while installing there it will ask you to select a partion either do the dual boot option (installing the other version of windows to a secondary partition) or install it on the partition windows Ult is already installed on. :)

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