Opening the right program with IE7

[xanadian9]

Here's the problem: If, for example. I have a PDF folder stored in My Documents, and double-click it, it will open with the correct program (Acrobat Reader 8). However, if I click on a PDF link in Internet Explorer, it wants to use a DIFFERENT version of Acrobat Reader, and thusly won't open it properly.

How do I fix this? I've stumbled upon the answer once before, but I can't find it now.