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Can I downgrade from Windows 7 Ultimate to Professional
Can I upgrade from Windows 7 Professional to ultimate



Windows 7 does not allow users to “downgrade” or convert from a more premium and more expensive edition to down-level, more basic and less expensive edition. For example, it’s impossible to downgrade from Windows 7 Ultimate to Windows 7 Professional or Enterprise, or from Windows 7 Professional to Windows 7 Home Premium or Home Basic.
Upgrade is only possible one-way from the lower edition to higher edition of Windows 7, and not the other way round. If user attempts to perform an in-place upgrade to downgrade to lesser edition of Windows 7
an error similar to below will be displayed at compatibility report: Windows 7 Ultimate cannot be upgraded to Windows 7 Home Premium. You can choose to install a new copy of Windows 7 Home Premium instead, but this is different from an upgrade, and does not keep your files, settings and programs. You’ll need to reinstall any programs using the original installation discs or files. To save your files before installing Windows, back them up to an external location such as a CD, DVD, or external hard drive. To install a new copy of Windows 7 Home Premium, click the Back button in the upper left-hand corner, and select “Custom (advanced)”. Microsoft probably forbids downgrade for a reason, such as possibility of corrupting or messing the operating system and complexity involved in such downgrade. For user who must perform in-place downgrade, there is a workaround trick that can force Windows 7 setup installer to allow “upgrade” or downgrade from uplevel edition of Windows 7 to downlevel version of Windows 7, while retaining all installed software, drivers and migrating all documents, music, video, shortcuts, bookmarks, favorites, and personal data files or settings.
These next few steps will walk you through a simple hack to downgrade any version easily.
A Windows 7 Ultimate Installation can normally not change into a minor version of "Windows 7 Home Premium" or "Professional". If you have installed a preview version of Windows 7 Ultimate (e.g. beta, release candidate build 7100 or RTM build 7600) and want to install a cheaper version Windows 7 Home Premium or Professional the installation is refused:

But with a change of a registry key whilst installation you can fake a minor version - so you can install the minor version
Change these registry keys ...

... into these for installing Windows 7 Professional ...

... or into these for installing Windows 7 Home Premium:

A re-boot after change of these registry keys is not necessary.
The version name to be entered must be identical to the version name on the installation DVD. See here the differences of an English and a German installation:


For downgrading do not boot from Windows 7 installation DVD.

Boot to Windows 7 and start "Setup.exe" from DVD; or after loading DVD the setup process starts automatically.

Start Upgrading (even this sounds absurd):



After successfully downgrading the welcome screen shows the new version:

Also the program "winver" shows the successfully downgrading:

All data, documents, music and movie files, installed driver and programs, shortcuts, program and user settings are retained. Only in a few Windows 7 programs some settings are reset to the initial settings; e.g. in the "services". After the downgrade the Windows 7 installation, of course, must be re-activated.
Attention: In Windows 7 Ultimate Build 7100 (Release Candidate) the effort is greater. First the entire DVD content must be copied to a folder to the hard drive. Then open in subfolder "sources" the file "cversion.ini" and change the entry "MinClient=7233.0" to "MinClient=7077.0". Then you can start the installation with "Setup.exe" (one folders hierarchy up). After the installation the entire folder can be deleted.