New
#301
Actually, that is one upgrade that you can do. I have successfully done an in-place repair install to switch my machine from en-us to en-gb base language. But that is only possible because you are changing the regional version of the same base language. It is not possible to change from Greek to English, as @Kari made me painfully aware a few years ago...
Changing system default language - Page 2 - Windows 10 ForumsWhen base language remains the same but is not the same regional version, Windows Setup warns about changing from one regional version of the language to another within same base language, yet allows user to keep installed software, settings and files.