I have a movie I made with QT Pro about 12 years ago. When I try to open it with the newest QT, as found in the newest OS on my newest (Ivy Bridge) MacBook, I get a message that I need to install QT 7. Huh? Is that right?
If this other 12 year old file also contains the same or similar "legacy" compression formats, then "yes," it is probably right.
The basic problem is that QT X is a completely re-written version of QT which only targets the playback of "modern" compression formats in specific file containers. Files made 12 years ago were created using codecs that were available at that time but which may not be supported by QT X which now supports codecs not supported by QT 7. (I.e., your web site file was compressed usinf Sorenson/Music compression (among other things) in an MOV file container. Therefore, Mountian Lion is suggesting that you install the QT 7 v7.6.6 Player app which still supports playback of this file in the older 32-bit mode which is still embedded in your Mountain Lion OS to maintain old (QT 7)/new (QT X) playback compatibility. (I.e., if you had the QT 7 player already installed, Mountain Lion would probably have simply asked if you wanted to switch to the QT 7 player for playback. (I.e., both QT X and QT 7 players can be simultaneously installed and used on your system if you leave them in their default install locations.)
Oddly, the Web version still plays:
The site may be relying on the older QT Plug-in.plugin for playback which is based on pre-QT X routines.
See QT 7 installation instructions for Lion/Mountain Lion HERE.