Any introduction to movies data flow ?

[Maurizio]

I'd like to know something basic about the general data flow
of movies under win2k/winxp.
Something as :
How many layers of software are needed ?
Where must every piece of software be registered (which reg keys?)
How is it possible to register a program like AviSynth that is
invoked "magically" under the scenes ?
What's the big picture of data encodig/decoding ?

Any suggestion ?
Regards.
Maurizio.