If you are trying to install QuickTime 7 and run into difficulty, see if your computer has QuickTime version 3 or 4 installed on it. If it does, uninstall QuickTime 3 or 4 completely before attempting to install QuickTime 7 again. Once the old version is gone, you should be able to install QuickTime 7 normally.
This document will be updated as more information becomes available.