Opening pdf's and jpg's outside of Netscape 7/Mozilla 1.1

[shedmeister]

When I double click on a pdf or jpg attachment in Netscape 7/Mozilla 1.1 mail, I'd like to have it open in my preferred image viewer (for jpg's) or Acrobat Reader outside of Netscape (for pdf's). Even if I define these helper applications in Preferences->Navigator->Helper Applications, the attachments still open in the browser or mail window. How can I change this?

Thanks,
Jim