Such an old thread. Yes it has been discussed many times since then lol
A video file that is 100 kb is going to be spam like porn or something.
Secondly & probably more relevant to you, QT player only comes with limited codecs (plug ins) that allow you to play different video formats. Thus either go chasing around trying to find them all, or else, we recommend this player: VLC - (click on link) _ (choose nearest mirror site) because it has all the codecs built into the player & is generally very reliable. To make it the default video player, see How to change default program in OSX

Heck I must be a slow typer. lmao