Microsoft Word shows this error if the global template (Normal.dot) is actually a Word document named Normal.dot. When Word tries to use the document as its default global template, you receive this error message.

To resolve this issue, click Yes on the message that follows the error message: Word has detected a problem with the existing normal.dot. Would you like to create a new normal.dot?
After you do this, a new Normal.dot template file is created and Word starts as expected.

If still same error occurs then you need word repair software to repair this file. you can try Stellar Phoenix Word Recovery Software from here: Word repair software repairs, recovers corrupted or damaged Ms Word document / .doc files , download the software and scan your word file, if you are able to view your word doument then opt for full version and save your file.