If you're trying to open them from within Word (using Word's Open dialog),
then Word is trying to open them as native files. You can right-click on a
file in Word's Open dialog and use Open With to select Adobe Reader or
Acrobat.
If you're opening them from My Documents and they're opening in Word, then
the .pdf file association needs to be repaired. Right-click on a PDF, choose
Open With, and select Adobe Reader or Acrobat if it's available. If not,
select "Choose Program..." In the Open With dialog, select Adobe Reader or
Acrobat, make sure that the box for "Always use the selected program to open
this kind of file" is checked, and click OK.
--
Suzanne S. Barnhill
Microsoft MVP (Word)
Words into Type
Fairhope, Alabama USA
http://word.mvps.org