It seems installing Office 2007 will eliminate the English dictionary from Outlook Express 6, often setting it to French. Microsoft recommends third party spell checkers, or moving to France. I’d say now is a good time to switch to a better email program like Thunderbird.
The MS Article: http://support.microsoft.com/kb/932974
While you are at that url, check out their shameless promotion of the lame ass Live.com search site:
“You can also use a search site to find spell-checking programs. For example, you can search for spell-checking programs at the following Web site: http://www.live.com”
Also, spell checking is not supported in the 64-bit version of Outlook Express.