Orphaned Application Path Entries
If you then uninstall or move the application the path entry in the registry becomes orphaned, i.e. it refers to an application that no longer exists. These path entries are completely useless and can be deleted safely.
Activating this option tells Registry Optimizer to search for such orphaned entries so that you can delete them.
Note: The actual paths to the applications are often valid even though the application files themselves no longer exist.