The title is a bit of a mouth full but basically states the nature of this tip. You may be noticing more files that are coming to your email that are the .docx kind and your word processing program can not open it. Text Edit can. Instead of going to File–>Open each time, you can set an application to always open with a certain file type. Here goes:
First, find a file that you want to change the program that opens it. Click once on it and hold down the key and the letter “i”. The following window appears. Under the Open With menu click on the drop down menu to select which program you want to open that file. If you want files like that one opened the same way check the box off that does so. My advice it to set Text Edit to open all .docx files Also, if you want Keynote to open all .ppt files (PowerPoint) you can do the same here.