Changing the language in Windows 8.1 single language

I followed the instructions in this question How to install a new "display language" onto Windows 8.1 Single Language? but now windows won't start properly, the screen is on but it's just black and I can see the cursor if I move it but I can't do anything else.

Solution 1:

This edition is not licensed to have multiple languages installed, because the licence policy entry Kernel-MUI-Number-Allowed only allows 1 language:

<sl:policyInt attributes="reboot-required, override-only" name="Kernel-MUI-Number-Allowed">1</sl:policyInt>

for the SingleLanguage SKU:

<sl:policyStr name="Kernel-EditionName">CoreSingleLanguage</sl:policyStr><sl:policyStr name="Kernel-CompositionEdition">CoreSingleLanguage</sl:policyStr>

Buy the normal Core edition which allows the install of new languages.