Recently I had to install/downgrade Windows 7 Ultimate to Professional without formatting or reinstalling OS on one of the friend’s computer. Though both are same Windows 7 family, it is not easy to switch the versions easily. The following method is to fake the Windows OS and tells that we have the professional version, then upgrade to the real version. The Ultimate version is the higher version of Windows 7 and it can’t be downgraded to lower versions officially without formatting or doing a fresh installation. Anyhow, I found a trick to downgrade Windows 7 ultimate to Professional easily without the new installation.
I’m not the owner of this trick, but I can confirm this works well.
Steps to Downgrade Windows 7 Ultimate to Professional
We are going to two 2 steps.
- Change registry key and tell Windows that we have the Professional version (Take extra precaution while modifying the registry, better take a backup of the registry before doing any changes)
- Insert the actual Windows 7 Professional CD and start the upgrade
Before starting the installation, just change two keys in Registry. It is like you are faking the Windows 7 installation that you are using the same version which you are going to install in next step. In my case, I had to change the key to ‘ Windows 7 Professional ’. Make sure you are typing the exact and correct OS version which is written on your installation DVD.
After you change the registry key, insert the Windows 7 Professional installation medium and start the upgrade.
Make sure you have enough of space in ‘System Partition’ (usually C drive). Allocate enough time since this will copy your personal data first, downgrade the OS and then copy back your data. If the computer data is so critical, I advise taking backup of your important data.
I suggest to clean up (move to the different location) your personal data (such as Desktop, My Documents..etc) before start the downgrade to save time.