Posted 08 August 2010 - 09:36 AM
First off, make sure you've got either Adobe Acrobat Reader or Foxit installed. (by going to your control panel > add/remove programs, or programs and features) If you don't have one of these programs, Google it and install one. Preferably Foxit.
Next, save a pdf directly to your desktop. Right-click it, and go to properties. In the section labeled "open with", click the change button. If you don't see Adobe Reader or Foxit in the list, click on Browse to choose a program to open it with and navigate to one of the two programs mentioned above. Usually in C:\Program Files\Foxit Software
Once you've chosen one of those programs, it should open normally for you.