Cannot View QT video but audio works

Ok, I have Quick Time Version 7.6.2
And there are some tutorial videos I need to watch
when I click on the video I want to watch a new screen opens
and a large QT viewer window opens, but it is black there is no video
but the audio plays. then a pop up window opens to inform me

Additional software is required for
QuickTime to play back this media. It may be
available (may be available)
from the QuickTime Components page.

Make sure your internet network connection
is active, then click the continue button to
check for software

So I do this and get taken to a page with several different
programs, but not given a clue as to which one I would need
to fix this problem
Can any body help Thanks

Andrew

 

Quick question before heading off to work
I just installed perian does it work by it self or do
I need to put in some settings, as I still have the same problem
when I start one of the videos, sorry for being such a nubie

Thanks again

Andrew

I just noticed that I cannot view the video tutorials on the Perian site but I do get a still frame amazon.com ad when the audio ends