1. Locate the Plugin Folder.Choose Go > Go To Folder from the menu bar in Finder, type /Library/Internet Plug-Ins in the search field, then click Go. The Internet Plug-Ins folder opens.
2. Move Files from Disabled Plugins folder.Notice several plugin files and a folder named Disabled Plugins. Copy these two files from the Disabled Plugins folder to the parent Internet Plug-Ins folder.
If you are ask to authenticate, click Authenticate, then enter an administrator name and password. Quit and open your browser again. The QuickTime plugin should now be active.