Run Registry Editor – regedit.exe (you can Click Start –> Run and then type regedit and finally press “Enter” )
2. Navigate to the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\MUI\UILanguages\xx-YY

where xx-YY is the original system user interface language locale string.For eg: it will be “en-US” for English US edition.

3. Rename the xx-YY to aa-BB, where aa-BB is the locale string for the new system language that you want to set (for eg: you can set it to “de-DE” for German), so that the registry key looks like below:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\MUI\UILanguages\aa-BB

4. Inside the renamed aa-BB registry key, create a new “String” value in the right pane, and name the new value data as DefaultFallback.
5. Assign the “DefaultFallback” with value of xx-YY (i.e. the original language).