To enable spell check in Word 10, go to the FILE tab at the top left-hand corner of your screen. From there, click Options and then Proofing. Ensure that the box for "Check spelling as you type" is checked. Then, click the "Recheck document" button that appears further down on the page.
You may also want to click the "AutoCorrect Options..." button near the bottom of the proofing menu. This will allow you to customize additional settings. For example, you can choose to have Word automatically replace certain misspelled words with the correct words as you type.
If you are still having issues with spell check, you may need to make sure that the proofing language is correctly set. To do this, go to Language Settings in the same Proofing menu and make sure that the language matches the one you are using in your document.
I hope this helps!