I used to install Microsoft Windows ony in English only although Slovenian language exist. Later I realized how rarely for small nation/language speaking people is to have their own language in Microsoft OS. Occasionally, due to the nature of the work still sometimes need English keyboard.
Yesterday someone came to me for advice on how to edit system language from Slovenian Windows 8.1 to primary English. Installing the keyboard was ok, but changing the system language was not. In the Control Panel, where we can add languages, only the english keyboard can be selected, but not entire language pack (MUI).
To help him and others, I post these links of MUI language packs.
Windows 8.1 64-bit
Windows 8.1 32-bit
It’s necessary to change the extension from * .cab to *.mlc. Right-click on the file and click on install.