I installed a Japanese version of windows 10 but then bought an English version and installed that after finding all the menus could not be changed to English during the install.

My question is does the English version overwrite the JP version or are files left on the SSD using up space?

Also in the end I returned the English version cause I found you can add a language pack to the JP version. The problem with this is that if you get a blue screen the Windows messages are in Japanese. So now unless I can change this I'm going to go back to an English version of Windows 10.