I don't know about the Word bit, but it sounds like it's connected to the default language.
Correct me if I'm wrong, but by base language I'm going to assume you mean the system is set to that language.
I don't know about other systems since I haven't done any language changing with them, but on Windows XP (And I'd assume other Windows OS) it would be...
Start > Control Panel > Date, Time, Language, and Regional Options > Regional and Language Options > Advanced
Seems to work for me if I need other languages for whatever reason (Say, to play foreign games or whatnot). It has, I've noticed, done things like changed my time format and made some webpages load in the selected languages, so if your computer is doing things like that...then it may help to try changing the language to one you recognize.