Unable to make Acrobat X the default handler/opener of PDF files on a Windows 8 laptop with Acrobat Reader also installed.

I have a user with a Windows 8 Sony Vaio laptop with Microsoft Office 2013 Professional, Acrobat X Standard, and Acrobat Reader installed. Another program on his system requires Acrobat Reader so we cannot just remove that and keep it off the system. Regardless of what he does to set the default program to open PDF files with, when he opens a PDF file it always opens it in Acrobat Reader and not Acrobat itself. We have re-associated it and set the default program handling repeatedly and have also tried complete uninstall and reinstall of both Acrobat and Acrobat Reader which had no effect on this. At this point I am of the opinion that this is a bug and the file association is being overridden somewhere in the registry besides the file association entries. Any help is appreciated.