How to change a file association in Windows. 
 
Problem: When you double click a file, the wrong program launches
to open the file, resulting in an error message of some type.
Solution:
   Change the program associated with the file extension.
To set the correct association between a file name extension and
the application used to edit that file type, do the following:
Open My Documents:  Select Folder Options... from the Tools Menu.
 
 
Select the File Types TAB, then scroll down the list till you see the file extension
you want to change.  In this example we are verifying that Acrobat opens files
with a PDF file Extension.  Once you find the file extension, if the wrong program
is listed next to the extension, Click the Change... Button to modify the association.
 
 
Clicking  the Change Button...above opens the dialog box shown below,
where you may choose the program you want to use to open the file type
selected in the previous dialog box.
 
 
Find the program that should open the selected file extension, select it and click OK.  Your done, close the windows.