https://answersrip.com/question/index?qid=20060919110328AAZUa6U
ok, when i try to search the answer itself from yahoo!answer, i found the above answer which i think it is the answer you are looking for.
answer from : low_on_ram
Best Answer - Chosen By Voters
Qoute:
Why doesn't spell check work?
Outlook Express supports the standard Microsoft spell check engine that is installed by Microsoft Office, Word, FrontPage, Works Suite and some other applications as part of Microsoft proofing tools. If you do not have one of those programs, the spell check in Outlook Express will not work. If you already have the spell check engine verify that Outlook Express is configured to check spelling:
Click Options on the Tools menu.
Click the Spelling tab.
Select the Always check spelling before sending check box. If you clear the box you can still use the spell check by pressing the F7 key.
If spell check still does not work, reinstall the newest application you have that includes the spell check engine.
Sometimes after installing an older version of the spell check engine, the spell check in Outlook Express stops working. That usually can be resolved by restoring a system file from your Windows XP CD-ROM, as described by MVP Michael Stevens.
Finally the spell check can be broken by missing or damaged entries in the Windows registry. There are two keys in particular that are prone to damage, and both can affect all versions of Outlook Express 5 and 6. The solutions are fairly easy and are documented in the Knowledge Base articles Spelling checker does not run on message in Outlook Express 5 and Spell Checker or Custom Dictionary Errors in Outlook Express.
Source(s):
http://www.microsoft.com/windows/ie/comm... "
If you do not satisfy with the answer, you can find again in YA. I found there are another 2 or 3 more the similar question, but i didn't go and check the answer.
Good luck !!