Equations written in Word 2003 or earlier cannot be edited in later versions of Word. If you are collaborating with other Word users, it's best to upgrade to a more recent version., From the top menu, select Insert → Object → Create New. If you see "Microsoft Equation 3.0" or "Math Type" in the Objects list, select it to insert an equation. Otherwise, go to the next step.Once you've inserted an equation, a small window will open with various symbols. Click these buttons and select the symbol you need to add it to the equation.
Word 2003 does not have the same formatting options as later versions. Some equations may look less professional than you're used to.
 If your copy of Word 2003 does not have one of the add-ins you mentioned above, you'll need to install one. It's not easy to locate these anymore, but fortunately the install package may already be waiting on your computer:Close all Microsoft Office programs.
Navigate to Start → Control Panel → Add or Remove Programs.
Select Microsoft Office → Change → Add or Remove Features → Next.
Click the + symbol next to Office Tools.
Select Equation Editor and click Run, then Update.
Follow onscreen instructions. If you're unlucky, you may need the Word 2003 install CD.
Know the limitations.
Attempt to insert an equation.
Install the add-in if necessary.
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