Problem with Equation Editor (Word)

Exactly what do you mean by "won't recognize 2003 equations"?

If you just see an empty rectangle in place of the equations, go to File>Options>Advanced>Show document content and uncheck the box for "Show picture placeholders".

When I open a Word 2003 file (using my Word 2013), the EQUATION sign on the upper line menu is no longer activated (that was not the case until a few days ago). Moreover, when I double click on any equation on the document... I get e message like ¨The program EQUATION is not isntalled on your computer or not responding¨.    

If I cant fix this, I would have to retype all equations from my old 2003 files (thousands) in the new 2013 Equation format. Thanks for any advise... it is much appreciated! 

You might try repairing the Office installation or remove all traces of the Office installation by downloading the fixit from the following article:

http://support.microsoft.com/kb/2739501

saving it to your computer and then running it.

Then reinstall Office by logging into www.office.com/myaccount with your registered email address and click Install Office.

Make sure that you have the necessary credentials to log in to your account before removing Office.