If either app has been deleted, you will have to re-install it. (The QT X Player is supposed to be in the 'Applications' folder and the QT 7 Player is supposed to be in your 'Applications/Utilities' folder if installed on your system. The normal thing to do here is to perform a search to see if the app in question was accidentally moved to a different location. These apps can easily be moved or deleted. On the other gand, QT Player X and QT Player 7 are apps that act as a graphic user interface to access the actual QT structure.
QT is a structure embedded in the operating system. I don't know when, or how, but Quicktime is no where to be seen on my iMac!
