I do not know if this applies to the other versions of the Office Suite 2007 set.
I do not know if this applies to the full version of Outlook.

But when I installed the Microsoft Office Home and Student 2007, it changed my spell check in Outlook Express to FRENCH, and will not allow me to choose any other language.

So far the only known solution is to BUY Proofing Tools for Microsoft 2003, according to the nice man I am sure was sitting in an office in India, safely outside the continental United State.

This is, by the way, a known bug and they are working on a solution.  He thinks.

Microsoft Office Home and Student 2007 does have a spellcheck in English, so I have no idea why it changed Outlook Express, which was not downloaded with it.

But trying to solve the problem has wasted two hours of my life that I'll never get back.

Thank you, Bill Gates.