You can use this document to guide you in changing your default programs based on windows file types.  This document references PDF file types but the same process can be used for any file type.

Right-click a .pdf file and go to Properties:

Where it says "Opens with:" click on the "Change ..." button 

In the menu that pops up select Adobe Acrobat (Reader or Pro) and hit OK:

Hit Apply and OK to close the window. Your PDF files should have the Adobe icon now and will open in Adobe when you double-click on them.