Windows 7: Corrected some file associations in Word 2010

I had Word assigned to open .pdf files (inadvertently). When Word would try to open these files, they opened but displayed gibberish. Instead of carefully thinking the problem through, I attributed the problem to an encoding setting. Since that wasn't the problem, there was no proper encoding that would read the files.



I have fixed the file association problem so any new documents open up correctly but I'm afraid I may have lost some documents because of changing the encoding on a Word file and compounding the problem by saving the files. It occurred to me that I did not know what the default Word encoding was supposed to be. Though there is an option for Windows (default), I'd like to know what the default is. I do not know enough about the subject to be familiar with terms like "unicode" and other options besides languages that are part of the scroll down menu. Their is also a set of radio buttons, I believe three one for Windows(default), one for MS-DOS, and a third whose title I cannot remember. I'm assuming that for all future use, Windows (default) is the correct option. I would like to know what that represents. Thanks to anyone who can help.