i've downloaded the correct movie for the score, i've put the score in the songs folder, i've put the movie named "movie.mp4" in the songs folder of the score folder, i've downloaded the k-lite codec stuff, i've made sure that the k-lite media player is my default. what am i doing wrong? someone please help!

while installing the K-Lite codec did you add the LAV Filters line?
...
it also has a built-in codec when installed!
...that's when your computer can't install its own LAV Filters when you install PPD game

i don't exactly know what you mean by LAV filters "line"? how do i do that?

As far as I know, when installing PPD it also has an option for the LAV Filter line...

PPD Game will run the movie file when Lav is successfully installed...

if not you still have to install K-Lite Codec...

Lav is also in there and i think it can force install and you will be able to play the game

As for the problem of not finding the movie, I can only think of the possibility that the chart file or your computer has some problem.