I had a similar problem except mine was with PowerPoint 2013.
A work computer had Office 2007 installed on it and needed to keep Outlook 2007 on the computer, so I did not uninstall Word, Excel or PowerPoint 2007. I then installed Office 2013 thinking it would default to the newest version. However this was not the case and no matter how many times I choose to "open with" PowerPoint 2013 and set it to the default open program, it would always open in 2007.
The trick was as techturtle described above except there was no POWERPNT.EXE key in the registry.
I had to go to:
- right click on the "Applications" folder and choose new and then choose key and type "POWERPNT.EXE"
- do this again, new key "shell"
- new key "command"
- new key "open"
so I created my own registry key for POWERPNT.EXE that looked like this
Once that was done I placed the location of the PowerPoint 2013 executable in the (Default) key. Which for me was:
"C:\Program Files\Microsoft Office 15\root\office15\POWERPNT.EXE" "%1"
* Update November 2014 *
I found recently that Windows did an update in early November 2014 that reverted everything back to Office 2007 as the default program again. This time I had to create the registry values for PowerPoint, Excel and Word as mentioned above. Once they were created, documents would still default to Office 2007. The final trick was to right click -> open with -> choose default program -> choose Office 2013 program. After creating the registry values you will find this option available.