A family of Microsoft word processing software products for creating web, email, and print documents.
Are you running two versions of Office on the same machine? In that case, you have to expect these constant "reconfigurations" as different versions of Word compete over file associations. To work around it, you set the NoRereg value in the registry to 1 for the version that you do not want to be the default. See the "Hacking the Registry" section in the article at http://www.gmayor.com/toolbars_in_word_2007.htm.
On the other hand, if you are running just one version of Office and you still see that error message, try starting Word as Administrator once, and see if that allows the configuration to complete once and for all. Here's how to do it: Exit Word 2013 if it is currently running. Click the Start button. In the search box, type winword; in the list of search results, right-click winword and choose the Run as Administrator.