Maybe try this...
It's a little messy but it works and it allows the user to skip the intro movie if they want...
And, after playing the game a few times the user will want to skip the intro...
Good luck...

Put this function above the main...

var avihandle;
function play_movie()
{
avihandle = media_play ("Movies/Your_Movie.wmv", NULL, 80);
while (media_playing (avihandle) != 0)
{
if (key_any != 0) // enable interrupting the intro by any key (recommend!)
{
media_stop (avihandle);
}
wait(1);
}

}

then put this in the main...

wait(1);
avihandle = media_play ("Your_Movie.wmv", NULL, 80);
wait(1);

while(mouse_left) { wait(1); } // check to see if mouse was not being held (so you cant skip the intro movie on accident)

enable_key = OFF;
enable_mouse = OFF;
enable_joystick = OFF;
while (media_playing (avihandle) != 0)
{
if (key_any != 0) // enable interrupting the intro by any key (recommend!)
{
media_stop (avihandle);
}
wait(1);
}
enable_key = ON;
enable_mouse = ON;
enable_joystick = ON;