If Microsoft Word does not detect spelling and grammar mistakes, check the Language settings. Are Proofing Tools installed? Is Speller add-in enabled?

If Microsoft Word's spell check isn't working, there are several common troubleshooting methods you can try.

How to Enable Spell Check in MS Office 2007. Microsoft Office 2007 checks your spelling and grammar by default. If it isn't checking your document, someone has disabled the feature.