I have a laptop loaded with Win 7 x86 and office 2010. Before Acrobat was installed I tried to open a PDF from within outlook (preview pane and open message) and when asked to choose a program with which to open it accidentally clicked windows media center.
After installing Acrobat all other PDFs can be opened via Acrobat and it is set as my system's default program. But each time I try to open a PDF from within outlook it opens it with WMC.
After uninstalling WMC nothing happens when you double click a PDF attachment in outlook.