Flash on a white board and slowdown problems

I am creating a flash project for a client which will need to be projected onto a white board from a laptop/desktop…this will be run in schools so the spec wont be amazing. Obviously the bigger the file… the better it will look when blown up on a white board. My problem is i have music and narative in the file and when i increase the dimensions to anything above 500 x 350 it starts to slow down and drop out of sync with the sound.

Because of the nature of the file there will be lots of space scenes…i.e. stars twinkling…asteroids etc…i’ve tried to only use tweens where nescessary as i know they draw on processor power. I suppose im just looking for the best solution as i’ve seen certain animations with a lot of details and sound which run fine…are these done frame by frame rather than with tweens…or does this still draw on processor power a lot.

the sound is set tyo stream and i have a preloader on or is it not realistic to have a full screen flash file.

And also this file needs a play and pause…both animation and sound…function which i implemented but unfortunately it causes my file to drop out of sync slightly after a few presses…does anyone know of a good play pause script.