Ahhh some of my swf's are 5mb

Some of my swf’s are massive and are taking ages to load, how can i go about reducing the file size, i mean swf’s should really only be about 10kb’s but mine are just huge, how do i solve this problem, i have heard about dynamically loaded images, how do i go about dynamically loading my images?

I visited the nike website, and they have all sorts of images and stuff, but their websites are very fast??Why is this??

any help would be appreciated.