Currently Being ModeratedOct 16, 2013 1:15 PM (in response to MarcheApple)
Where did the videos come from? Do they play correctly in QuickTime Player? The problem may be the type of videos you're trying to play, test with something from the iTunes Store.
Also, make sure you've tried the sugggestions in this Apple doc -> Troubleshooting iTunes for Windows Vista or Windows 7 video playback performance issues