No, you don’t need to change a setting. Quicktime 10 is basically a movie player, and lacks the QTVR abilities of earlier Quicktime versions. When you installed Quicktime 7, those abilities were then available for for Quicktime 10 to use. (BTW, Quicktime 7 isn’t that old - there was no QT8 or QT9) This is just Apple slowly taking features away from Quicktime, and there is no harm in having both on your system.

That said, one of the best things you can do for the future is render your projects out as “equirectangular” images and use a tool like Pano2VR ( http://gardengnomesoftware.com/pano2vr.php ) to convert that image to a Flash VR or HTML5 VR (for things like iPhones and iPads which don’t support Flash). The image file can also be saved to create new formats whenever those come up in the future…