A question of computer speed

I have a flash movie that is loading external movies into it when buttons are pressed. I figured this way it will load faster.

However, I’ve noticed that on some computers the external movies run rather slow and on other computers they run normal speed.

My question: is this something that has to do with individual computers and there is really nothing I can do about it? I’ve messed with the frame rate and such but it doesn’t do a whole lot.