Dear Peter,
May I know whether the issue occurs suddenly? If yes, what did you do before the issue occurred?
Does the Word application crash only when you insert the equation? If you use other features, will the Word application crash?
As Online Repair may fix some general issues, I suggest you go to Control Panel>Programs>right-click on the Office applications' icon>Change>check whether there is an Online Repair option. If yes, run it, restart the computer and do a test again to see and let us know the result.
May I know whether there are some add-ins installed on your Word application? If you run Word in Safe Mode via the steps in Open Office apps in safe mode on a Windows PC - Microsoft Support, what's the outcome?
Does the issue occur with a specific file?
If it is convenient, I suggest you close all Office applications, open Run, type %appdata%\Microsoft\Templates, move the Normal.dotm file out, restart the Word application and create a new file to see the outcome.
Moreover, please click on File>Account and upload a full screenshot of the Account page in the Word application for our reference.
Note: Remove any private information before uploading the screenshots.
Welcome to share any updates at your convenience if you need further help on this issue.
Thanks for your effort and time.
Sincerely
Cliff | Microsoft Community Moderator