Suggestion:
go back into folder options, highlight the .pdf file extention and click on edit, see if there is "OPEN" anywhere in the new window.
if there is, click on it (to highlite it) again click on edit IN THAT window and check out the path to the Acrobat's exe file
if this ISN'T one, click on new, in the window that opens type in "Open" in the "Action" box and click on the next box "Appliction which performs function" click on browse, find the directory for the Acrobat's Exe file that you'll use to OPEN the .pdf file, select OK once you've highlighted the exe file, select ALL OKs and close up the View File Types till you're back in explorer, and that should take care of redirecting the Wind's open pointer.
Good luck--
MiggyD