Odds are, your computer does not have the correct plug-in to play those files. Plug-ins tell your browser or media player how to read certain media files. For instance, if you’re using a Windows PC, chances are you have no problem viewing Windows Media files, but you probably can’t watch QuickTime movies. To watch them, you will need to download and install the latest version of QuickTime. To learn more about plug-ins, see our Installing Plug-Ins guide.