Since MetaTrader 4 Client Terminal doesn't support Unicode, the required language must be specified as a language for non-unicode applications on Windows operating system settings.
1. Open Control Panel, click Clock, Language, and Region link, and then click Region and Language option.
2. In the Region and Language window go to the Administrative tab.
3. In the Language for non-Unicode programs section set the language of non-Unicode programs that will be used.
4. When you’re done selecting the language, click OK. You are now informed that you need to restart your PC or device so that the change gets applied.
5. Close all your open applications and documents and click Restart now.
When you log back in, the new language is applied for non-Unicode programs.