Office 2007 Language Problems

Hey there. I think I have some language problems on Microsoft Office Enterprise 2007. Sometimes when I do use thesaurus a message pops up saying "No thesaurus available for Irish (Gaeilge). This is bad because some words I enter are spelt wrong in English and the spell checker doesn't catch it because my language is set to Irish. Is there any way to get rid of this in all of Office, including Powerpoint and Excel and all others? I want to make the default language on Office English. Thanks in advance!