When you say the prices you gave before, you mean the ones here: After: SYSTEM\ControlSet00X\Control\MUI\UILanguages\el-GR Type = 408 SYSTEM\ControlSet00X\Control\Nls\Language\ Default = 0408 InstallLanguage = 0408 SYSTEM\ControlSet00X\Control\Nls\Locale\ Default = 0408 (Default) = 0408
Yes, however you need the MUI files in these directories otherwise system will break: C:\Windows\el-GR C:\Windows\System32\el-GR C:\Windows\SysWOW64\el-GR (if 64-Bit) Also, I recommend you to do that on WinPE environment. Regedit might not allow you to edit these values when you're logged in. Also for any possible breaks, I recommend you to backup the SYSTEM file located in Windows\system32\config. Edit: Wait for me, I'll send a screenshot as an example.
Not needed. You can do everything safely on the live OS. I don't think those reg places are especially protected, but in the worst case just launch regedit as trusted installer (using nsudo, runasTI or alike). On the other hand some directories (like \windows\boot or \windows\system32\boot) are protected, so if you want to be precise and add the MUIs also there, you need to use something like XY explorer launched as TI)