In my personal experience, I have had trouble viewing several fan films on my PC. Why? The best way I can explain it is this: Microsoft and Apple don't play nice with each other. Most films you will find are in .mov or .avi formats. Vista has a hard time running .mov, but that's the most popular format for film makers. So, instead of downloading Quick Time, get the VLC Player. You can get it for free HERE

I can't say enough good things about this player!
Once you get it, there's a small trick.
You'll need to do the following:
Settings
Preferences
Video
Output Modules
check Advanced Options
choose Windows GDI video output