Ive downloaded movie clips that are suposed to play on quicktime, but when i play them, it just opens quicktime with a white screen. It has the right length shown at the bottom, but theres no sound or picture. I just updated my quicktime and now i dont know what to do.How do i make them play?

Doesn't it say anything when you try to open said files?
Like, giving you a new window saying that QT lacks some codecs to play the file and that those codecs might be available on the QT site?

Anyway, even if it doesn't, I still suggest downloading VLC and/or Mplayer (both free. You can find them here and here respecitvely).
Those two can play virtually any video/audio format and have features that Quicktime doesn't, unless you go Pro (like Fullscreen).

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